Merge pull request #6949 from dcw803/master

imported my solutions to both tasks in C and Perl

14 files changed, 1010 insertions, 23 deletions

diff --git a/challenge-187/duncan-c-white/C/.cbuild b/challenge-187/duncan-c-white/C/.cbuild
index 624a95ebfb..a14ec76520 100644
--- a/challenge-187/duncan-c-white/C/.cbuild
+++ b/challenge-187/duncan-c-white/C/.cbuild
@@ -1,4 +1,4 @@
-BUILD = ch-1
+BUILD = ch-1 ch-2
 CFLAGS = -Wall -g
 #LDFLAGS = -lm
 #CFLAGS = -g
diff --git a/challenge-187/duncan-c-white/C/Makefile b/challenge-187/duncan-c-white/C/Makefile
new file mode 100644
index 0000000000..34d8a4d520
--- /dev/null
+++ b/challenge-187/duncan-c-white/C/Makefile
@@ -0,0 +1,18 @@
+# Makefile rules generated by CB
+CC	= gcc
+CFLAGS	= -Wall -g
+BUILD	= ch-1 ch-2
+
+all:	$(BUILD)
+
+clean:
+	/bin/rm -f $(BUILD) *.o core a.out
+
+args.o:	args.c
+ch-1:	ch-1.o args.o
+ch-1.o:	ch-1.c args.h
+ch-2:	ch-2.o args.o parseints.o printarray.o
+ch-2.o:	ch-2.c args.h parseints.h printarray.h
+parseints.o:	parseints.c args.h parseints.h printarray.h
+printarray.o:	printarray.c
+
diff --git a/challenge-187/duncan-c-white/C/README b/challenge-187/duncan-c-white/C/README
new file mode 100644
index 0000000000..b7043e9cbb
--- /dev/null
+++ b/challenge-187/duncan-c-white/C/README
@@ -0,0 +1,11 @@
+Thought I'd also have a go at translating ch-1.pl into C..
+
+Of course, it can only deal with lists of integers, so the original
+examples have to change.
+
+It produce identical (non-debugging) output to my Perl original.
+
+It uses several of my regular support modules:
+- a command-line argument processing module args.[ch],
+- a csvlist-of-int parsing module parseints.[ch], and
+- an int-array printing module printarray.[ch].
diff --git a/challenge-187/duncan-c-white/C/args.c b/challenge-187/duncan-c-white/C/args.c
new file mode 100644
index 0000000000..d4a2d38b9a
--- /dev/null
+++ b/challenge-187/duncan-c-white/C/args.c
@@ -0,0 +1,207 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <ctype.h>
+#include <assert.h>
+
+
+bool debug = false;
+
+
+// process_flag_noarg( name, argc, argv );
+//	Process the -d flag, and check that there are no
+//	remaining arguments.
+void process_flag_noarg( char *name, int argc, char **argv )
+{
+	int arg=1;
+	if( argc>1 && strcmp( argv[arg], "-d" ) == 0 )
+	{
+		debug = true;
+		arg++;
+	}
+
+	int left = argc-arg;
+	if( left != 0 )
+	{
+		fprintf( stderr, "Usage: %s [-d]\n", name );
+		exit(1);
+	}
+}
+
+
+// int argno = process_flag_n_args( name, argc, argv, n, argmsg );
+//	Process the -d flag, and check that there are exactly
+//	n remaining arguments, return the index position of the first
+//	argument.  If not, generate a fatal Usage error using the argmsg.
+//	
+int process_flag_n_args( char *name, int argc, char **argv, int n, char *argmsg )
+{
+	int arg=1;
+	if( argc>1 && strcmp( argv[arg], "-d" ) == 0 )
+	{
+		debug = true;
+		arg++;
+	}
+
+	int left = argc-arg;
+	if( left != n )
+	{
+		fprintf( stderr, "Usage: %s [-d] %s\n       Exactly %d "
+			"arguments needed\n", name, argmsg, n );
+		exit(1);
+	}
+	return arg;
+}
+
+
+// int argno = process_flag_n_m_args( name, argc, argv, min, max, argmsg );
+//	Process the -d flag, and check that there are between
+//	min and max remaining arguments, return the index position of the first
+//	argument.  If not, generate a fatal Usage error using the argmsg.
+//	
+int process_flag_n_m_args( char *name, int argc, char **argv, int min, int max, char *argmsg )
+{
+	int arg=1;
+	if( argc>1 && strcmp( argv[arg], "-d" ) == 0 )
+	{
+		debug = true;
+		arg++;
+	}
+
+	int left = argc-arg;
+	if( left < min || left > max )
+	{
+		fprintf( stderr, "Usage: %s [-d] %s\n       Between %d and %d "
+			"arguments needed\n", name, argmsg, min, max );
+		exit(1);
+	}
+	return arg;
+}
+
+
+// process_onenumarg_default( name, argc, argv, defvalue, &n );
+//	Process the -d flag, and check that there is a single
+//	remaining numeric argument (or no arguments, in which case
+//	we use the defvalue), putting it into n
+void process_onenumarg_default( char *name, int argc, char **argv, int defvalue, int *n )
+{
+	char argmsg[100];
+	sprintf( argmsg, "[int default %d]", defvalue );
+	int arg = process_flag_n_m_args( name, argc, argv, 0, 1, argmsg );
+
+	*n = arg == argc ? defvalue : atoi( argv[arg] );
+}
+
+
+// process_onenumarg( name, argc, argv, &n );
+//	Process the -d flag, and check that there is a single
+//	remaining numeric argument, putting it into n
+void process_onenumarg( char *name, int argc, char **argv, int *n )
+{
+	int arg = process_flag_n_args( name, argc, argv, 1, "int" );
+
+	// argument is in argv[arg]
+	*n = atoi( argv[arg] );
+}
+
+
+// process_twonumargs( name, argc, argv, &m, &n );
+//	Process the -d flag, and check that there are 2
+//	remaining numeric arguments, putting them into m and n
+void process_twonumargs( char *name, int argc, char **argv, int *m, int *n )
+{
+	int arg = process_flag_n_args( name, argc, argv, 2, "int" );
+
+	// arguments are in argv[arg] and argv[arg+1]
+	*m = atoi( argv[arg++] );
+	*n = atoi( argv[arg] );
+}
+
+
+// process_twostrargs() IS DEPRECATED: use process_flag_n_m_args() instead
+
+
+// int arr[100];
+// int nel = process_listnumargs( name, argc, argv, arr, 100 );
+//	Process the -d flag, and check that there are >= 2
+//	remaining numeric arguments, putting them into arr[0..nel-1]
+//	and returning nel.
+int process_listnumargs( char *name, int argc, char **argv, int *arr, int maxel )
+{
+	int arg=1;
+	if( argc>1 && strcmp( argv[arg], "-d" ) == 0 )
+	{
+		debug = true;
+		arg++;
+	}
+
+	int left = argc-arg;
+	if( left < 2 )
+	{
+		fprintf( stderr, "Usage: %s [-d] list_of_numeric_args\n", name );
+		exit(1);
+	}
+	if( left > maxel )
+	{
+		fprintf( stderr, "%s: more than %d args\n", name, maxel );
+		exit(1);
+	}
+
+	// elements are in argv[arg], argv[arg+1]...
+
+	if( debug )
+	{
+		printf( "debug: remaining arguments are in arg=%d, "
+		        "firstn=%s, secondn=%s..\n",
+			arg, argv[arg], argv[arg+1] );
+	}
+
+	int nel = 0;
+	for( int i=arg; i<argc; i++ )
+	{
+		arr[nel++] = atoi( argv[i] );
+	}
+	arr[nel] = -1;
+	return nel;
+}
+
+
+//
+// bool isint = check_unsigned_int( char *val, int *n );
+//	Given an string val, check that there's an unsigned integer
+//	in it (after optional whitespace).  If there is a valid
+//	unsigned integer value, store that integer value in *n and
+//	return true; otherwise return false (and don't alter *n).
+bool check_unsigned_int( char *val, int *n )
+{
+	// skip whitespace in val
+	char *p;
+	for( p=val; isspace(*p); p++ )
+	{
+		/*EMPTY*/
+	}
+	if( ! isdigit(*p) ) return false;
+	*n = atoi(p);
+	return true;
+}
+
+
+//
+// bool ok = check_unsigned_real( char *val, double *n );
+//	Given an string val, check that there's an unsigned real
+//	in it (after optional whitespace).  If there is a valid
+//	unsigned real value, store that value in *n and
+//	return true; otherwise return false (and don't alter *n).
+bool check_unsigned_real( char *val, double *n )
+{
+	// skip whitespace in val
+	char *p;
+	for( p=val; isspace(*p); p++ )
+	{
+		/*EMPTY*/
+	}
+	if( ! isdigit(*p) ) return false;
+	*n = atof(p);
+	return true;
+}
diff --git a/challenge-187/duncan-c-white/C/args.h b/challenge-187/duncan-c-white/C/args.h
new file mode 100644
index 0000000000..8844a8f9c4
--- /dev/null
+++ b/challenge-187/duncan-c-white/C/args.h
@@ -0,0 +1,11 @@
+extern bool debug;
+
+extern void process_flag_noarg( char * name, int argc, char ** argv );
+extern int process_flag_n_args( char * name, int argc, char ** argv, int n, char * argmsg );
+extern int process_flag_n_m_args( char * name, int argc, char ** argv, int min, int max, char * argmsg );
+extern void process_onenumarg_default( char * name, int argc, char ** argv, int defvalue, int * n );
+extern void process_onenumarg( char * name, int argc, char ** argv, int * n );
+extern void process_twonumargs( char * name, int argc, char ** argv, int * m, int * n );
+extern int process_listnumargs( char * name, int argc, char ** argv, int * arr, int maxel );
+extern bool check_unsigned_int( char * val, int * n );
+extern bool check_unsigned_real( char * val, double * n );
diff --git a/challenge-187/duncan-c-white/C/ch-1.c b/challenge-187/duncan-c-white/C/ch-1.c
new file mode 100644
index 0000000000..c94c3e9bd8
--- /dev/null
+++ b/challenge-187/duncan-c-white/C/ch-1.c
@@ -0,0 +1,116 @@
+//
+// Task 1: Days Together
+// 
+// C version.
+// 
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <ctype.h>
+#include <assert.h>
+
+#include "args.h"
+//#include "parseints.h"
+//#include "printarray.h"
+
+
+int dim[] = { -1, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
+
+// int day_in_year = yearday( ddmm );
+//     Check whether $ddmm is a valid date of format dd-mm where dd is 1..31
+//	and mm is 1..12 (and dd <= days_in_month(mm)), returning the day number
+//	in the year if it is, or -1 if it is invalid.
+//
+int yearday( char *ddmm )
+{
+	// validate overall shape /^(\d\d?)-(\d\d?)$/
+	int d, m;
+	if( sscanf( ddmm, "%d-%d", &d, &m ) != 2 ) return -1;
+
+	if( m < 1 || m > 12 ) return -1;
+
+	if( d < 1 || d > dim[m] ) return -1;
+
+	int dayno = 0;
+	for( int i=1; i<m; i++ )
+	{
+		dayno += dim[i];
+	}
+	dayno += d;
+	return dayno;
+}
+
+
+#define min(a,b)  ((a)<(b)?(a):(b))
+#define max(a,b)  ((a)>(b)?(a):(b))
+
+
+//
+//
+// int noverlap = overlapdays( sd1d, ed1d, sd2d, ed2d );
+//	Find out the number of overlapping days between the two ranges
+//	of dates, as the task describes.  Each date is represented by
+//	a logical day-number-in-the-year.  Return 0 if no overlap.
+int overlapdays( int sd1d, int ed1d, int sd2d, int ed2d )
+{
+	// none if one range finishes before the other
+	if( ed1d < sd2d || ed2d < sd1d ) return 0;
+
+	int csd = max(sd1d,sd2d); // common start date
+	int ced = min(ed1d,ed2d); // common end date
+
+	return 1+ced-csd;
+}
+
+
+int main( int argc, char **argv )
+{
+	int argno = process_flag_n_args( "overlapping-days", argc, argv,
+		4, "dd-mm-sd1 dd-mm-ed1 dd-mm-sd2 dd-mm-ed2" );
+
+	if( debug )
+	{
+		printf( "debug: argno=%d, firstarg=%s\n", argno, argv[argno] );
+	}
+
+	char *date = argv[argno++];
+	int sd1d = yearday( date ); // days since start of year for sd1
+	if( sd1d < 1 )
+	{
+		fprintf( stderr, "Bad dd-mm-sd1 (%s)\n", date );
+		exit(1);
+	}
+
+	date = argv[argno++];
+	int ed1d = yearday( date ); // days since start of year for ed1
+	if( ed1d < 1 )
+	{
+		fprintf( stderr, "Bad dd-mm-ed1 (%s)\n", date );
+		exit(1);
+	}
+
+	date = argv[argno++];
+	int sd2d = yearday( date ); // days since start of year for sd2
+	if( sd2d < 1 )
+	{
+		fprintf( stderr, "Bad dd-mm-sd2 (%s)\n", date );
+		exit(1);
+	}
+
+	date = argv[argno++];
+	int ed2d = yearday( date ); // days since start of year for ed2
+	if( ed2d < 1 )
+	{
+		fprintf( stderr, "Bad dd-mm-ed2 (%s)\n", date );
+		exit(1);
+	}
+
+	printf( "sd1:%d, ed1:%d, sd2:%d, ed2:%d\n", sd1d, ed1d, sd2d, ed2d );
+
+	int noverlap = overlapdays( sd1d, ed1d, sd2d, ed2d );
+	printf( "%d days\n", noverlap );
+
+	return 0;
+}
diff --git a/challenge-187/duncan-c-white/C/ch-2.c b/challenge-187/duncan-c-white/C/ch-2.c
new file mode 100644
index 0000000000..5d3eeb6cd7
--- /dev/null
+++ b/challenge-187/duncan-c-white/C/ch-2.c
@@ -0,0 +1,188 @@
+//
+// Task 2: Magical Triplets
+// 
+// C version.
+// 
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <ctype.h>
+#include <assert.h>
+
+#include "args.h"
+#include "parseints.h"
+#include "printarray.h"
+
+
+typedef struct {
+	int a, b, c;
+	int sum;	// computed field: a+b+c
+} triplet;
+
+
+typedef struct		// a dynamic list of triplets
+{
+	int n, max;
+	int maxsum;
+	triplet *t;	// dynarray t[max] allocated, t[0..n-1] in use
+} tlist;
+
+
+// tlist t;
+// bool alreadyseen = add_tlist( a, b, c, &t );
+//	Add the triple (a,b,c) to tlist t unless it's already
+//	present.  Return true if it was already present, else return false.
+bool add_tlist( int a, int b, int c, tlist *t )
+{
+	for( int i=0; i<t->n; i++ )
+	{
+		triplet *p = &(t->t[i]);
+		if( p->a == a && p->b == b && p->c == c )
+		{
+			return true;
+		}
+	}
+	// not found, add (a,b,c) to t
+	if( t->n == t->max )
+	{
+		t->max += 100;
+		t->t = realloc( t->t, t->max );
+		assert( t->t != NULL );
+	}
+	triplet *p = &(t->t[t->n++]);
+	p->a = a;
+	p->b = b;
+	p->c = c;
+	// keep track of triplet sum, and tlist maxsum so far
+	p->sum = a+b+c;
+	if( p->sum > t->maxsum )
+	{
+		t->maxsum = p->sum;
+	}
+	return false;
+}
+
+
+// showtlist( FILE *out, char *name, tlist *t );
+//	Display t on out.
+void showtlist( FILE *out, char *name, tlist *t )
+{
+	fprintf( out, "%s has %d triples, max sum=%d\n",
+		name, t->n, t->maxsum );
+	for( int i=0; i<t->n; i++ )
+	{
+		triplet *p = &(t->t[i]);
+		fprintf( out, "%d+%d+%d=%d\n", p->a, p->b, p->c, p->sum );
+	}
+}
+
+
+// freetlist( t );
+//	Free the tlist t.
+void freetlist( tlist *t )
+{
+	free( t->t );
+	free( t );
+}
+
+
+// tlist *t = pass1( x, nel );
+//	generate all triples of 3 distinct elements in x (in
+//	any order) and find those triples that pass rules 1..3,
+//	building and returning a tlist t of the triplets found.
+//	Note that a tlist keeps track of the triplet sums, and
+//	even the current maximum sum, so it's more like pass1+2
+//	of the original Perl code.
+//	Note that the returned value t must be freed by the caller after use.
+//
+tlist *pass1( int *x, int nel )
+{
+	tlist *result = malloc( sizeof(tlist) );
+	assert( result != NULL );
+	result->max = 100;
+	result->n = 0;
+	result->maxsum = 0;
+	result->t = malloc( result->max * sizeof(triplet) );
+	assert( result->t != NULL );
+
+	for( int p1=0; p1<nel; p1++ )
+	{
+		for( int p2=0; p2<nel; p2++ )
+		{
+			if( p1==p2 ) continue;
+			for( int p3=0; p3<nel; p3++ )
+			{
+				if( p1==p3 || p2==p3 ) continue;
+				int a = x[p1];
+				int b = x[p2];
+				int c = x[p3];
+				if( a+b<=c || b+c<=a || a+c<=b ) continue;
+				if( add_tlist( a, b, c, result ) ) continue;
+				if( debug )
+				{
+					printf( "debug: semi-magic triple %d, %d, %d, sum=%d\n", a, b, c, a+b+c );
+					//showtlist( stdout, "s-m-ts", result );
+				}
+			}
+		}
+	}
+
+	return result;
+}
+
+
+int main( int argc, char **argv )
+{
+	int argno = process_flag_n_args( "magic-triple", argc, argv,
+		1, "csvlist" );
+
+	if( debug )
+	{
+		printf( "debug: argno=%d, firstarg=%s\n", argno, argv[argno] );
+	}
+
+	int nel;
+	int *x = parse_int_args( argc, argv, argno, &nel );
+	nel--;
+
+	if( nel<3 )
+	{
+		fprintf( stderr, "magic-triple: csvlist %s must contain at least 3 numbers\n", argv[argno] );
+		exit(1);
+	}
+
+	if( debug )
+	{
+		printf( "nel=%d, x=", nel );
+		print_int_array( 70, nel, x, ',', stdout );
+		putchar( '\n' );
+	}
+
+	// pass 1 - generate all triples of 3 distinct elements in x (in
+	//	    any order) and find those triples that pass rules 1..3
+	tlist *p1t = pass1( x, nel );
+	showtlist( stdout, "pass1 triples", p1t );
+
+	// if there are NO triplets found obeying rules 1..3, report failure
+	if( p1t->n == 0 )
+	{
+		printf( "No magic triplets found\n" );
+		exit(0);
+	}
+
+	// pass2: identify which of those triples has the maxsum && has a>=b>=c
+	for( int i=0; i<p1t->n; i++ )
+	{
+		triplet *p = &(p1t->t[i]);
+		if( p->sum != p1t->maxsum ) continue;
+		if( p->a < p->b || p->b < p->c ) continue;
+		printf( "Found magic triple %d, %d, %d\n", p->a, p->b, p->c );
+	}
+
+	freetlist( p1t );
+
+	free( x );
+	return 0;
+}
diff --git a/challenge-187/duncan-c-white/C/parseints.c b/challenge-187/duncan-c-white/C/parseints.c
new file mode 100644
index 0000000000..1b188afe8d
--- /dev/null
+++ b/challenge-187/duncan-c-white/C/parseints.c
@@ -0,0 +1,105 @@
+// Simple routine to parse one or more arguments,
+// looking for individual +ints or comma-separated
+// lists of +ints.
+// 
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <ctype.h>
+#include <assert.h>
+
+#include "args.h"
+#include "printarray.h"
+#include "parseints.h"
+
+typedef struct
+{
+	int nel;	// current number of elements 
+	int maxel;	// maximum number of elements allocated
+	int *list;	// malloc()d list of integers
+} intlist;
+
+
+//
+// intlist il.. then initialize il..  then:
+// add_one( element, &il );
+//	
+static void add_one( int x, intlist *p )
+{
+	if( p->nel > p->maxel )
+	{
+		p->maxel += 128;
+		p->list = realloc( p->list, p->maxel );
+		assert( p->list );
+	}
+	if( debug )
+	{
+		printf( "PIA: appending %d to result at "
+			"pos %d\n", x, p->nel );
+	}
+	p->list[p->nel++] = x;
+}
+
+
+//
+// intlist il.. then initialize il..  then:
+// add_one_arg( argstr, &il );
+//	
+static void add_one_arg( char *argstr, intlist *p )
+{
+	int x;
+	if( !check_unsigned_int(argstr,&x) )
+	{
+		fprintf( stderr, "PIA: arg %s must be +int\n", argstr );
+		exit(1);
+	}
+	add_one( x, p );
+}
+
+
+//
+// int nel;
+// int *ilist = parse_int_args( argc, argv, argno, &nel );
+//	process all arguments argv[argno..argc-1], extracting either
+//	single ints or comma-separated lists of ints from those arguments,
+//	accumulate all integers in a dynarray list, storing the total number
+//	of elements in nel.  This list must be freed by the caller.
+int *parse_int_args( int argc, char **argv, int argno, int *nel )
+{
+	int *result = malloc( 128 * sizeof(int) );
+	assert( result );
+	intlist il = { 0, 128, result };
+
+	if( debug )
+	{
+		printf( "PIA: parsing ints from args %d..%d\n", argno, argc-1 );
+	}
+	for( int i=argno; i<argc; i++ )
+	{
+		assert( strlen(argv[i]) < 1024 );
+		char copy[1024];
+		strcpy( copy, argv[i] );
+		char *com;
+		char *s;
+		for( s=copy; (com = strchr(s,',')) != NULL; s=com+1 )
+		{
+			*com = '\0';
+			add_one_arg( s, &il );
+		}
+		add_one_arg( s, &il );
+	}
+
+	add_one( -1, &il );
+
+	if( debug )
+	{
+		printf( "PIA: final list is " );
+		print_int_array( 80, il.nel, il.list, ',', stdout );
+		putchar( '\n' );
+	}
+
+	*nel = il.nel;
+	return il.list;
+}
diff --git a/challenge-187/duncan-c-white/C/parseints.h b/challenge-187/duncan-c-white/C/parseints.h
new file mode 100644
index 0000000000..da5e145a86
--- /dev/null
+++ b/challenge-187/duncan-c-white/C/parseints.h
@@ -0,0 +1 @@
+extern int * parse_int_args( int argc, char ** argv, int argno, int * nel );
diff --git a/challenge-187/duncan-c-white/C/printarray.c b/challenge-187/duncan-c-white/C/printarray.c
new file mode 100644
index 0000000000..ddee597df3
--- /dev/null
+++ b/challenge-187/duncan-c-white/C/printarray.c
@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <string.h>
+
+
+// print_int_array( maxw, nelements, results[], sep, outfile );
+//	format results[0..nelements-1] as a <sep> separated
+//      list onto outfile with lines <= maxw chars long.
+//	produces a whole number of lines of output - without the trailing '\n'
+void print_int_array( int maxw, int nel, int *results, char sep, FILE *out )
+{
+	int linelen = 0;
+	for( int i=0; i<nel; i++ )
+	{
+		char buf[100];
+		sprintf( buf, "%d", results[i] );
+		int len = strlen(buf);
+		if( linelen + len + 2 > maxw )
+		{
+			fputc( '\n', out );
+			linelen = 0;
+		} else if( i>0 )
+		{
+			fputc( ' ', out );
+			linelen++;
+		}
+
+		linelen += len;
+		fprintf( out, "%s", buf );
+		if( i<nel-1 )
+		{
+			fputc( sep, out );
+			linelen++;
+		}
+	}
+	//if( linelen>0 )
+	//{
+	//	fputc( '\n', out );
+	//}
+}
diff --git a/challenge-187/duncan-c-white/C/printarray.h b/challenge-187/duncan-c-white/C/printarray.h
new file mode 100644
index 0000000000..40efb83277
--- /dev/null
+++ b/challenge-187/duncan-c-white/C/printarray.h
@@ -0,0 +1 @@
+extern void print_int_array( int maxw, int nel, int * results, char sep, FILE * out );
diff --git a/challenge-187/duncan-c-white/README b/challenge-187/duncan-c-white/README
index 44c69614fa..ce8d8f7676 100644
--- a/challenge-187/duncan-c-white/README
+++ b/challenge-187/duncan-c-white/README
@@ -1,40 +1,89 @@
-Task 1: Zip List
+Task 1: Days Together
 
-You are given two list @a and @b of same size.
-Create a subroutine sub zip(@a, @b) that merge the two list as shown in
-the example below.
+Two friends, Foo and Bar gone on holidays seperately to the same city. You
+are given their schedule i.e. start date and end date.
 
-Example
+To keep the task simple, the date is in the form DD-MM and all dates
+belong to the same calendar year i.e. between 01-01 and 31-12. Also the
+year is non-leap year and both dates are inclusive.
 
-Input:  @a = qw/1 2 3/; @b = qw/a b c/;
-Output: zip(@a, @b) should return qw/1 a 2 b 3 c/;
-        zip(@b, @a) should return qw/a 1 b 2 c 3/;
+Write a script to find out for the given schedule, how many days they
+spent together in the city, if at all.
 
+Example 1
+
+Input: Foo => SD: '12-01' ED: '20-01'
+       Bar => SD: '15-01' ED: '18-01'
+
+Output: 4 days
+
+Example 2
+
+Input: Foo => SD: '02-03' ED: '12-03'
+       Bar => SD: '13-03' ED: '14-03'
+
+Output: 0 day
+
+Example 3
+
+Input: Foo => SD: '02-03' ED: '12-03'
+       Bar => SD: '11-03' ED: '15-03'
+
+Output: 2 days
 
-MY NOTES: very easy, except for the fact that a Perl subroutine CAN'T
-take 2 arrays.  Guess he meant array-refs?
+Example 4
+
+Input: Foo => SD: '30-03' ED: '05-04'
+       Bar => SD: '28-03' ED: '02-04'
+
+Output: 4 days
+
+MY NOTES: pretty easy.  Let's do it by hand (no Date modules to inc-date)
+given all the constraints, same year, non-leap year.
 
 GUEST LANGUAGE: As a bonus, I also had a go at translating ch-1.pl
-into C (look in the C directory for that).  Of course, that could
-only deal with lists of integers, so the examples above have to change.
+into C (look in the C directory for that).
+
+
+Task 2: Magical Triplets
 
+You are given a list of positive numbers, @n, having at least 3 numbers.
 
-Task 2: Unicode Makeover
+Write a script to find the triplets (a, b, c) from the given list that
+satisfies the following rules.
 
-You are given a string with possible unicode characters.
-Create a subroutine sub makeover($str) that replace the unicode characters with ascii equivalent. For this task, let us assume it only contains alphabets.
+1. a + b > c
+2. b + c > a
+3. a + c > b
+4. a + b + c is maximum.
+
+In case, you end up with more than one triplets having the maximum then
+pick the triplet where a >= b >= c.
 
 Example 1
 
-Input: $str = 'ÃÊÍÒÙ';
-Output: 'AEIOU'
+    Input: @n = (1, 2, 3, 2);
+    Output: (3, 2, 2)
 
 Example 2
 
-Input: $str = 'âÊíÒÙ';
-Output: 'aEiOU'
+    Input: @n = (1, 3, 2);
+    Output: ()
+
+Example 3
+
+    Input: @n = (1, 1, 2, 3);
+    Output: ()
+
+Example 4
+
+    Input: @n = (2, 4, 3);
+    Output: (4, 3, 2)
 
+MY NOTES: Ok, sounds like generate+test.  Find all triples. Find
+triples that pass tests (1)..(3).  Then find which triples have the
+maximum sum.  If only, that's the answer.  If more than one, use the
+tie break rule.
 
-MY NOTES: Unicode: just say no - hell no.
-My terminal doesn't even display the horrible input strings right.
-I'm not doing this.  Forget it.
+GUEST LANGUAGE: As a bonus, I also had a go at translating ch-2.pl
+into C (look in the C directory for that).
diff --git a/challenge-187/duncan-c-white/perl/ch-1.pl b/challenge-187/duncan-c-white/perl/ch-1.pl
new file mode 100755
index 0000000000..4de13bf986
--- /dev/null
+++ b/challenge-187/duncan-c-white/perl/ch-1.pl
@@ -0,0 +1,127 @@
+#!/usr/bin/perl
+# 
+# Task 1: Days Together
+# 
+# Two friends, Foo and Bar gone on holidays seperately to the same city. You
+# are given their schedule i.e. start date and end date.
+# 
+# To keep the task simple, the date is in the form DD-MM and all dates
+# belong to the same calendar year i.e. between 01-01 and 31-12. Also the
+# year is non-leap year and both dates are inclusive.
+# 
+# Write a script to find out for the given schedule, how many days they
+# spent together in the city, if at all.
+# 
+# Example 1
+# 
+# Input: Foo => SD: '12-01' ED: '20-01'
+#        Bar => SD: '15-01' ED: '18-01'
+# 
+# Output: 4 days
+# 
+# Example 2
+# 
+# Input: Foo => SD: '02-03' ED: '12-03'
+#        Bar => SD: '13-03' ED: '14-03'
+# 
+# Output: 0 day
+# 
+# Example 3
+# 
+# Input: Foo => SD: '02-03' ED: '12-03'
+#        Bar => SD: '11-03' ED: '15-03'
+# 
+# Output: 2 days
+# 
+# Example 4
+# 
+# Input: Foo => SD: '30-03' ED: '05-04'
+#        Bar => SD: '28-03' ED: '02-04'
+# 
+# Output: 4 days
+# 
+# MY NOTES: pretty easy.  Let's do it by hand (no Date modules to inc-date)
+# given all the constraints, same year, non-leap year.
+# 
+# GUEST LANGUAGE: As a bonus, I also had a go at translating ch-1.pl
+# into C (look in the C directory for that).
+# 
+
+use strict;
+use warnings;
+use feature 'say';
+use feature 'state';
+use Getopt::Long;
+use Data::Dumper;
+use List::Util qw(min max);
+use Function::Parameters;
+
+
+my $debug=0;
+die "Usage: overlapping-days [--debug] dd-mm-sd1 dd-mm-ed1 dd-mm-sd2 dd-mm-ed2\n"
+	unless GetOptions( "debug"=>\$debug ) && @ARGV==4;
+
+
+my @dim = ( -1, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 );
+
+=pod
+
+=head2 my $day_in_year = yearday( $ddmm );
+
+Check whether $ddmm is a valid date of format dd-mm where dd is 1..31
+and mm is 1..12 (and dd <= days_in_month(mm)), returning the day number
+in the year if it is, or -1 if it is invalid.
+
+=cut
+fun yearday( $ddmm )
+{
+	return -1 unless $ddmm =~ /^(\d\d?)-(\d\d?)$/;
+	my( $d, $m ) = ( $1, $2 );
+	return -1 if $m < 1 || $m > 12;
+	return -1 if $d < 1 || $d > $dim[$m];
+	my $dayno = 0;
+	for( my $i=1; $i<$m; $i++ )
+	{
+		$dayno += $dim[$i];
+	}
+	$dayno += $d;
+	return $dayno;
+}
+
+
+my( $sd1, $ed1, $sd2, $ed2 ) = @ARGV;
+my $sd1d = yearday( $sd1 ); # days since start of year for sd1
+die "Bad dd-mm-sd1 ($sd1)\n" if $sd1d<1;
+my $ed1d = yearday( $ed1 );
+die "Bad dd-mm-ed1 ($ed1)\n" if $ed1d<1;
+my $sd2d = yearday( $sd2 );
+die "Bad dd-mm-sd2 ($sd2)\n" if $sd2d<1;
+my $ed2d = yearday( $ed2 );
+die "Bad dd-mm-ed2 ($ed2)\n" if $ed2d<1;
+
+say "sd1:$sd1d, ed1:$ed1d, sd2:$sd2d, ed2:$ed2d";
+
+
+=pod
+
+=head2 my $noverlap = overlapdays( $sd1d, $ed1d, $sd2d, $ed2d );
+
+Find out the number of overlapping days between the two ranges
+of dates, as the task describes.  Each date is represented by a logical
+day-number-in-the-year.  Return 0 if no overlap.
+
+=cut
+fun overlapdays( $sd1d, $ed1d, $sd2d, $ed2d )
+{
+	# none if one range finishes before the other
+	return 0 if $ed1d < $sd2d || $ed2d < $sd1d;
+
+	my $csd = max($sd1d,$sd2d); # common start date
+	my $ced = min($ed1d,$ed2d); # common end date
+
+	return 1+$ced-$csd;
+}
+
+
+my $noverlap = overlapdays( $sd1d, $ed1d, $sd2d, $ed2d );
+say "$noverlap days";
diff --git a/challenge-187/duncan-c-white/perl/ch-2.pl b/challenge-187/duncan-c-white/perl/ch-2.pl
new file mode 100755
index 0000000000..04e0ffe055
--- /dev/null
+++ b/challenge-187/duncan-c-white/perl/ch-2.pl
@@ -0,0 +1,114 @@
+#!/usr/bin/perl
+# 
+# Task 2: Magical Triplets
+# 
+# You are given a list of positive numbers, @n, having at least 3 numbers.
+# 
+# Write a script to find the triplets (a, b, c) from the given list that
+# satisfies the following rules.
+# 
+# 1. a + b > c
+# 2. b + c > a
+# 3. a + c > b
+# 4. a + b + c is maximum.
+# 
+# In case, you end up with more than one triplets having the maximum then
+# pick the triplet where a >= b >= c.
+# 
+# Example 1
+# 
+#     Input: @n = (1, 2, 3, 2);
+#     Output: (3, 2, 2)
+# 
+# Ex