here are my solutions to last week's challenge (oops), in Perl and C

13 files changed, 852 insertions, 26 deletions

diff --git a/challenge-199/duncan-c-white/C/Makefile b/challenge-199/duncan-c-white/C/Makefile
new file mode 100644
index 0000000000..bf2d32d1a1
--- /dev/null
+++ b/challenge-199/duncan-c-white/C/Makefile
@@ -0,0 +1,19 @@
+# Makefile rules generated by CB
+CC	= gcc
+CFLAGS	= -Wall -g
+LDFLAGS	= -lm
+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 parseints.o printarray.o
+ch-1.o:	ch-1.c args.h parseints.h printarray.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-199/duncan-c-white/C/README b/challenge-199/duncan-c-white/C/README
new file mode 100644
index 0000000000..5f960417f8
--- /dev/null
+++ b/challenge-199/duncan-c-white/C/README
@@ -0,0 +1,9 @@
+Thought I'd also have a go at translating ch-1.pl and ch-2.pl into C..
+
+Both C versions produce near-identical (non-debugging and even debugging)
+output to the Perl originals.
+
+They use 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-199/duncan-c-white/C/args.c b/challenge-199/duncan-c-white/C/args.c
new file mode 100644
index 0000000000..d4a2d38b9a
--- /dev/null
+++ b/challenge-199/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-199/duncan-c-white/C/args.h b/challenge-199/duncan-c-white/C/args.h
new file mode 100644
index 0000000000..8844a8f9c4
--- /dev/null
+++ b/challenge-199/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-199/duncan-c-white/C/ch-1.c b/challenge-199/duncan-c-white/C/ch-1.c
new file mode 100644
index 0000000000..2f42f40f25
--- /dev/null
+++ b/challenge-199/duncan-c-white/C/ch-1.c
@@ -0,0 +1,114 @@
+//
+// Task 1: Good Pairs
+// 
+// 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 i, j;
+} pair;
+
+
+typedef struct {
+	int npairs;	// number of pairs.
+	int nalloc;	// number of pairs allocated (nalloc >= npairs)
+	pair *p;	// block to store up to <nalloc> pairs, of which
+			// the first <npairs> are in use at present.
+} pairdynarray;
+
+
+void init_pairdynarray( pairdynarray *p )
+{
+	p->npairs = 0;
+	p->nalloc = 10;
+	p->p = malloc( p->nalloc * sizeof(pair) );
+	assert( p->p != NULL );
+}
+
+
+void add_pair( pairdynarray *p, int i, int j )
+{
+	p->npairs++;
+	if( p->npairs == p->nalloc )
+	{
+		p->nalloc += 10;
+		p->p = realloc( p->p, p->nalloc * sizeof(pair) );
+		assert( p->p != NULL );
+	}
+	p->p[p->npairs].i = i;
+	p->p[p->npairs].j = j;
+}
+
+
+void free_pairdynarray( pairdynarray *p )
+{
+	if( p->p != NULL ) free( p->p );
+	p->p = NULL;
+}
+
+
+int main( int argc, char **argv )
+{
+	int argno = process_flag_n_m_args( "good-pairs", argc, argv,
+		1, 1000, "intlist" );
+
+	int nel;
+	int *list = parse_int_args( argc, argv, argno, &nel );
+
+	if( nel < 1 )
+	{
+		fprintf( stderr, "good-pairs: need a list of > 0 elements\n" );
+		exit(1);
+	}
+
+	if( debug )
+	{
+		printf( "debug: initial list: " );
+		print_int_array( 60, nel, list, ',', stdout );
+		putchar( '\n' );
+	}
+
+	pairdynarray p;
+	init_pairdynarray( &p );
+
+	for( int i=0; i<nel; i++ )
+	{
+		for( int j=i+1; j<nel; j++ )
+		{
+			if( list[i] != list[j] ) continue;
+
+			add_pair( &p, i, j );
+		}
+	}
+
+	if( debug )
+	{
+		printf( "debug: npairs=%d, nalloc=%d\n", p.npairs, p.nalloc );
+	} else
+	{
+		printf( "%d\n", p.npairs );
+	}
+
+	printf( "Good pairs are below:\n" );
+	for( int n=0; n<p.npairs; n++ )
+	{
+		printf( "(%d,%d)\n", p.p[n].i, p.p[n].j );
+	}
+
+	free( list );
+	free_pairdynarray( &p );
+
+	return 0;
+}
diff --git a/challenge-199/duncan-c-white/C/ch-2.c b/challenge-199/duncan-c-white/C/ch-2.c
new file mode 100644
index 0000000000..97cb50b648
--- /dev/null
+++ b/challenge-199/duncan-c-white/C/ch-2.c
@@ -0,0 +1,134 @@
+//
+// Task 2: Good 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 i, j, k;
+} triple;
+
+
+typedef struct {
+	int ntriples;	// number of triples.
+	int nalloc;	// number of triples allocated (nalloc >= ntriples)
+	triple *p;	// block to store up to <nalloc> triples, of which
+			// the first <ntriples> are in use at present.
+} tripledynarray;
+
+
+void init_tripledynarray( tripledynarray *t )
+{
+	t->ntriples = 0;
+	t->nalloc = 10;
+	t->p = malloc( t->nalloc * sizeof(triple) );
+	assert( t->p != NULL );
+}
+
+
+void add_triple( tripledynarray *t, int i, int j, int k )
+{
+	t->ntriples++;
+	if( t->ntriples == t->nalloc )
+	{
+		t->nalloc += 10;
+		t->p = realloc( t->p, t->nalloc * sizeof(triple) );
+		assert( t->p != NULL );
+	}
+	t->p[t->ntriples].i = i;
+	t->p[t->ntriples].j = j;
+	t->p[t->ntriples].k = k;
+}
+
+
+void free_tripledynarray( tripledynarray *t )
+{
+	if( t->p != NULL ) free( t->p );
+	t->p = NULL;
+}
+
+
+int main( int argc, char **argv )
+{
+	int argno = process_flag_n_m_args( "good-triples", argc, argv,
+		4, 1000, "intlist" );
+
+	int x = atoi( argv[argno++] );
+	int y = atoi( argv[argno++] );
+	int z = atoi( argv[argno++] );
+
+	if( debug )
+	{
+		printf( "debug: x=%d, y=%d, z=%d\n", x, y, z );
+	}
+
+	int nel;
+	int *list = parse_int_args( argc, argv, argno, &nel );
+
+	if( nel < 3 )
+	{
+		fprintf( stderr, "good-triples: need a list of > 2 elements\n" );
+		exit(1);
+	}
+
+	if( debug )
+	{
+		printf( "debug: initial list: " );
+		print_int_array( 60, nel, list, ',', stdout );
+		putchar( '\n' );
+	}
+
+	tripledynarray t;
+	init_tripledynarray( &t );
+
+	for( int i=0; i<nel; i++ )
+	{
+		for( int j=i+1; j<nel; j++ )
+		{
+			if( abs(list[i]-list[j]) > x ) continue;
+
+			for( int k=j+1; k<nel; k++ )
+			{
+				if( abs(list[j]-list[k]) <= y &&
+				    abs(list[i]-list[k]) <= z )
+				{
+				  add_triple( &t, list[i], list[j], list[k] );
+				}
+			}
+		}
+	}
+
+	if( debug )
+	{
+		printf( "debug: ntriples=%d, nalloc=%d\n", t.ntriples, t.nalloc );
+	} else
+	{
+		printf( "%d\n", t.ntriples );
+	}
+
+	if( t.ntriples > 0 )
+	{
+		printf( "Good triples are below:\n" );
+		for( int n=0; n<t.ntriples; n++ )
+		{
+			printf( "(%d,%d)\n", t.p[n].i, t.p[n].j );
+		}
+	}
+
+	free( list );
+	free_tripledynarray( &t );
+
+	return 0;
+}
diff --git a/challenge-199/duncan-c-white/C/parseints.c b/challenge-199/duncan-c-white/C/parseints.c
new file mode 100644
index 0000000000..0fb9985633
--- /dev/null
+++ b/challenge-199/duncan-c-white/C/parseints.c
@@ -0,0 +1,114 @@
+// 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 0
+	if( debug )
+	{
+		printf( "PIA: appending %d to result at "
+			"pos %d\n", x, p->nel );
+	}
+	#endif
+	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.
+//	Note that the list of elements used to be terminated by a -1 value,
+//	but I've commented this out from now on.
+//
+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 0
+	if( debug )
+	{
+		printf( "PIA: parsing ints from args %d..%d\n", argno, argc-1 );
+	}
+	#endif
+	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 0
+	if( debug )
+	{
+		printf( "PIA: final list is " );
+		print_int_array( 80, il.nel, il.list, ',', stdout );
+		putchar( '\n' );
+	}
+	#endif
+
+	*nel = il.nel;
+	return il.list;
+}
diff --git a/challenge-199/duncan-c-white/C/parseints.h b/challenge-199/duncan-c-white/C/parseints.h
new file mode 100644
index 0000000000..da5e145a86
--- /dev/null
+++ b/challenge-199/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-199/duncan-c-white/C/printarray.c b/challenge-199/duncan-c-white/C/printarray.c
new file mode 100644
index 0000000000..ddee597df3
--- /dev/null
+++ b/challenge-199/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-199/duncan-c-white/C/printarray.h b/challenge-199/duncan-c-white/C/printarray.h
new file mode 100644
index 0000000000..40efb83277
--- /dev/null
+++ b/challenge-199/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-199/duncan-c-white/README b/challenge-199/duncan-c-white/README
index dffa7605cf..11114219fc 100644
--- a/challenge-199/duncan-c-white/README
+++ b/challenge-199/duncan-c-white/README
@@ -1,58 +1,78 @@
-Task 1: Max Gap
+Task 1: Good Pairs
 
 You are given a list of integers, @list.
 
-Write a script to find the total pairs in the sorted list where 2
-consecutive elements has the max gap. If the list contains less then 2
-elements then return 0.
+Write a script to find the total count of Good Pairs: A pair (i, j) is
+called good if list[i] == list[j] and i < j.
+
 
 Example 1
 
-Input:  @list = (2,5,8,1)
-Output: 2
+Input: @list = (1,2,3,1,1,3)
+Output: 4
 
-Since the sorted list (1,2,5,8) has 2 such pairs (2,5) and (5,8)
+There are 4 good pairs found as below:
+(0,3)
+(0,4)
+(3,4)
+(2,5)
 
 Example 2
 
-Input: @list = (3)
+Input: @list = (1,2,3)
 Output: 0
 
+Example 3
+
+Input: @list = (1,1,1,1)
+Output: 6
 
-MY NOTES: very easy.  sort, then sequence through the sorted list,
-finding the max gap so far and all pairs with that gap.
+Good pairs are below:
+(0,1)
+(0,2)
+(0,3)
+(1,2)
+(1,3)
+(2,3)
+
+MY NOTES: very easy.  two nested for loops..
 
 GUEST LANGUAGE: As a bonus, I also had a go at translating ch-1.pl
 into C (look in the C directory for the translation)
 
 
-Task 2: Prime Count
+Task 2: Good Triplets
 
-You are given an integer $n > 0.
+You are given an array of integers, @array and three integers $x,$y,$z.
 
-Write a script to print the count of primes less than $n.
-Example 1
+Write a script to find out total Good Triplets in the given array.
 
-Input: $n = 10
-Output: 4 as in there are 4 primes less than 10 are 2, 3, 5 ,7.
+A triplet array[i], array[j], array[k] is good if it satisfies the following conditions:
 
-Example 2
+a) 0 <= i < j < k <= n (size of given array)
+b) abs(array[i] - array[j]) <= x
+c) abs(array[j] - array[k]) <= y
+d) abs(array[i] - array[k]) <= z
 
-Input: $n = 15
-Output: 6
+Example 1
 
-Example 3
+Input: @array = (3,0,1,1,9,7) and $x = 7, $y = 2, $z = 3
+Output: 4
+
+Good Triplets are as below:
+(3,0,1) where (i=0, j=1, k=2)
+(3,0,1) where (i=0, j=1, k=3)
+(3,1,1) where (i=0, j=2, k=3)
+(0,1,1) where (i=1, j=2, k=3)
+
+Example 2
 
-Input: $n = 1
+Input: @array = (1,1,2,2,3) and $x = 0, $y = 0, $z = 1
 Output: 0
 
-Example 4
 
-Input: $n = 25
-Output: 9
 
-MY NOTES: very easy, specially if you have a prime finding module lying
-around:-)
+MY NOTES: not quite so easy, start with 3 nested for loops;-)
 
 GUEST LANGUAGE: As a bonus, I also had a go at translating ch-2.pl
 into C (look in the C directory for the translation)
diff --git a/challenge-199/duncan-c-white/perl/ch-1.pl b/challenge-199/duncan-c-white/perl/ch-1.pl
new file mode 100755
index 0000000000..a088c95e6b
--- /dev/null
+++ b/challenge-199/duncan-c-white/perl/ch-1.pl
@@ -0,0 +1,77 @@
+#!/usr/bin/perl
+# 
+# Task 1: Good Pairs
+# 
+# You are given a list of integers, @list.
+# 
+# Write a script to find the total count of Good Pairs: A pair (i, j) is
+# called good if list[i] == list[j] and i < j.
+# 
+# 
+# Example 1
+# 
+# Input: @list = (1,2,3,1,1,3)
+# Output: 4
+# 
+# There are 4 good pairs found as below:
+# (0,3)
+# (0,4)
+# (3,4)
+# (2,5)
+# 
+# Example 2
+# 
+# Input: @list = (1,2,3)
+# Output: 0
+# 
+# Example 3
+# 
+# Input: @list = (1,1,1,1)
+# Output: 6
+# 
+# Good pairs are below:
+# (0,1)
+# (0,2)
+# (0,3)
+# (1,2)
+# (1,3)
+# (2,3)
+# 
+# MY NOTES: very easy.  two nested for loops..
+# 
+# GUEST LANGUAGE: As a bonus, I also had a go at translating ch-1.pl
+# into C (look in the C directory for the translation)
+# 
+
+use strict;
+use warnings;
+use feature 'say';
+use Getopt::Long;
+use Data::Dumper;
+
+my $debug=0;
+die "Usage: good-pairs [--debug] intlist\n"
+	unless GetOptions( "debug"=>\$debug ) && @ARGV>0;
+
+my @list = split( /,/, join(',',@ARGV) );
+
+die "good-pairs: need at least 2 ints in list\n" unless @list>1;
+
+my @result;
+
+for( my $i=0; $i<@list; $i++ )
+{
+	for( my $j=$i+1; $j<@list; $j++ )
+	{
+		push @result, [$i,$j] if $list[$i] == $list[$j];
+	}
+}
+
+say scalar(@result);
+
+say "Good pairs are below:";
+foreach my $p (@result)
+{
+	my( $i, $j ) = @$p;
+	say "($i,$j)";
+}
diff --git a/challenge-199/duncan-c-white/perl/ch-2.pl b/challenge-199/duncan-c-white/perl/ch-2.pl
new file mode 100755
index 0000000000..a189381668
--- /dev/null
+++ b/challenge-199/duncan-c-white/perl/ch-2.pl
@@ -0,0 +1,80 @@
+#!/usr/bin/perl
+# 
+# Task 2: Good Triplets
+# 
+# You are given an array of integers, @array and three integers $x,$y,$z.
+# 
+# Write a script to find out total Good Triplets in the given array.
+# 
+# A triplet array[i], array[j], array[k] is good if it satisfies the following conditions:
+# 
+# a) 0 <= i < j < k <= n (size of given array)
+# b) abs(array[i] - array[j]) <= x
+# c) abs(array[j] - array[k]) <= y
+# d) abs(array[i] - array[k]) <= z
+# 
+# Example 1
+# 
+# Input: @array = (3,0,1,1,9,7) and $x = 7, $y = 2, $z = 3
+# Output: 4
+# 
+# Good Triplets are as below:
+# (3,0,1) where (i=0, j=1, k=2)
+# (3,0,1) where (i=0, j=1, k=3)
+# (3,1,1) where (i=0, j=2, k=3)
+# (0,1,1) where (i=1, j=2, k=3)
+# 
+# Example 2
+# 
+# Input: @array = (1,1,2,2,3) and $x = 0, $y = 0, $z = 1
+# Output: 0
+# 
+# MY NOTES: not quite so easy, start with 3 nested for loops;-)
+# 
+# GUEST LANGUAGE: As a bonus, I also had a go at translating ch-2.pl
+# into C (look in the C directory for the translation)
+#
+
+use strict;
+use warnings;
+use feature 'say';
+use Getopt::Long;
+use Function::Parameters;
+use Data::Dumper;
+
+my $debug=0;
+die "Usage: good-triplets [--debug] X,Y.and Z intlist\n"
+	unless GetOptions( "debug"=>\$debug ) && @ARGV > 4;
+my( $x, $y, $z, @list ) = @ARGV;
+
+@list = split( /,/, join(',',@list) );
+
+die "good-triples: need at least 3 ints in list\n" unless @list>2;
+
+my @result;
+
+for( my $i=0; $i<@list; $i++ )
+{
+	for( my $j=$i+1; $j<@list; $j++ )
+	{
+		next if abs($list[$i] - $list[$j]) > $x;
+		for( my $k=$j+1; $k<@list; $k++ )
+		{
+			push @result, [$list[$i],$list[$j],$list[$k] ] if
+				abs($list[$j] - $list[$k]) <= $y &&
+				abs($list[$i] - $list[$k]) <= $z;
+		}
+	}
+}
+
+say scalar(@result);
+
+if( @result )
+{
+	say "Good triples are below:";
+	foreach my $p (@result)
+	{
+		my( $i, $j, $k ) = @$p;
+		say "($i,$j,$k)";
+	}
+}