Merge pull request #7533 from dcw803/master

(belatedly did and) committed my solutions to this challenge

27 files changed, 1839 insertions, 56 deletions

diff --git a/challenge-202/duncan-c-white/C/Makefile b/challenge-202/duncan-c-white/C/Makefile
new file mode 100644
index 0000000000..bf2d32d1a1
--- /dev/null
+++ b/challenge-202/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-202/duncan-c-white/C/README b/challenge-202/duncan-c-white/C/README
new file mode 100644
index 0000000000..e0fb8e8359
--- /dev/null
+++ b/challenge-202/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 most 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-202/duncan-c-white/C/args.c b/challenge-202/duncan-c-white/C/args.c
new file mode 100644
index 0000000000..d4a2d38b9a
--- /dev/null
+++ b/challenge-202/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-202/duncan-c-white/C/args.h b/challenge-202/duncan-c-white/C/args.h
new file mode 100644
index 0000000000..8844a8f9c4
--- /dev/null
+++ b/challenge-202/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-202/duncan-c-white/C/ch-1.c b/challenge-202/duncan-c-white/C/ch-1.c
new file mode 100644
index 0000000000..2717ff2db9
--- /dev/null
+++ b/challenge-202/duncan-c-white/C/ch-1.c
@@ -0,0 +1,84 @@
+//
+// Task 1: Consecutive Odds
+// 
+// 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"
+
+
+// bool isodd = isodd( x );
+//	Return 1 iff x is odd; else 0.
+//
+bool isodd( int x )
+{
+	return x % 2 == 1;
+}
+
+
+//
+// bool hasodds = has3odds( list, nel );
+//	Return true iff list has 3 consecutive odd numbers; else false.
+//
+bool has3odds( int *list, int nel )
+{
+	for( int i=0; i<nel-2; i++ )
+	{
+		if( ! isodd( list[i] ) ) continue;
+		if( debug )
+		{
+			printf( "debug: found odd element %d at pos %d\n",
+				list[i], i );
+		}
+		if( isodd( list[i+1] ) && isodd( list[i+2] ) )
+		{
+			if( debug )
+			{
+				printf( "debug: found 3 consec odd elements "
+				        "%d, %d, %d starting at pos %d\n",
+				        list[i], list[i+1], list[i+2], i );
+			}
+			return true;
+		}
+	}
+	return false;
+}
+
+
+int main( int argc, char **argv )
+{
+	int argno = process_flag_n_m_args( "3-consec-odds", argc, argv,
+		1, 1000, "intlist" );
+
+	int nel;
+	int *list = parse_int_args( argc, argv, argno, &nel );
+
+	if( nel < 3 )
+	{
+		fprintf( stderr, "3-consec-odds: need a list of > 2 elements\n" );
+		exit(1);
+	}
+
+	if( debug )
+	{
+		printf( "debug: initial list: " );
+		print_int_array( 60, nel, list, ',', stdout );
+		putchar( '\n' );
+	}
+
+	bool hasodds = has3odds( list, nel );
+	printf( "%d\n", (int)hasodds );
+
+	free( list );
+
+	return 0;
+}
diff --git a/challenge-202/duncan-c-white/C/ch-2.c b/challenge-202/duncan-c-white/C/ch-2.c
new file mode 100644
index 0000000000..af2845861e
--- /dev/null
+++ b/challenge-202/duncan-c-white/C/ch-2.c
@@ -0,0 +1,90 @@
+//
+// Task 2: Widest Valley
+// 
+// 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 len = find_valley( spos, list, nel );
+//	find the leftmost longest sequence of one or more adjacent numbers
+//	where initially the numbers go down (or stay the same) and then they
+//	go up (or stay the same).
+//
+int find_valley( int spos, int *list, int nel )
+{
+	int curr = list[spos];
+	int p = spos+1;
+	for( ; p<nel && list[p] <= curr; curr=list[p++] )
+	{
+	}
+	for( ; p<nel && list[p] >= curr; curr=list[p++] )
+	{
+	}
+	if( debug )
+	{
+		printf( "debug: found valley from pos %d to pos %d\n",
+			spos, p-1 );
+	}
+	return p-spos;
+}
+
+
+int main( int argc, char **argv )
+{
+	int argno = process_flag_n_m_args( "widest-valley", argc, argv,
+		1, 1000, "intlist" );
+	int nel;
+	int *list = parse_int_args( argc, argv, argno, &nel );
+
+	if( nel == 0 )
+	{
+		fprintf( stderr, "widest-valley: need a list of > 0 elements\n" );
+		exit(1);
+	}
+
+	if( debug )
+	{
+		printf( "debug: initial list: " );
+		print_int_array( 60, nel, list, ',', stdout );
+		putchar( '\n' );
+	}
+
+	int maxw = 0;
+	int maxw_spos = 0;
+
+	for( int spos=0; spos<nel; spos++ )
+	{
+		int w = find_valley( spos, list, nel );
+		if( w > maxw )
+		{
+			if( debug )
+			{
+				printf( "debug: found new widest valley "
+					"starting at %d: width %d\n", spos, w );
+			}
+			maxw = w;
+			maxw_spos = spos;
+		}
+	}
+
+	for( int i=0; i<maxw; i++ )
+	{
+		if( i>0 ) printf( ", " );
+		printf( "%d", list[maxw_spos+i] );
+	}
+	putchar( '\n' );
+
+	free( list );
+	return 0;
+}
diff --git a/challenge-202/duncan-c-white/C/parseints.c b/challenge-202/duncan-c-white/C/parseints.c
new file mode 100644
index 0000000000..0fb9985633
--- /dev/null
+++ b/challenge-202/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-202/duncan-c-white/C/parseints.h b/challenge-202/duncan-c-white/C/parseints.h
new file mode 100644
index 0000000000..da5e145a86
--- /dev/null
+++ b/challenge-202/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-202/duncan-c-white/C/printarray.c b/challenge-202/duncan-c-white/C/printarray.c
new file mode 100644
index 0000000000..ddee597df3
--- /dev/null
+++ b/challenge-202/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-202/duncan-c-white/C/printarray.h b/challenge-202/duncan-c-white/C/printarray.h
new file mode 100644
index 0000000000..40efb83277
--- /dev/null
+++ b/challenge-202/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-202/duncan-c-white/README b/challenge-202/duncan-c-white/README
index 28f5718a9a..c6dd8b8b1c 100644
--- a/challenge-202/duncan-c-white/README
+++ b/challenge-202/duncan-c-white/README
@@ -1,52 +1,72 @@
-Task 1: Missing Numbers
+Task 1: Consecutive Odds
 
-You are given an array of unique numbers.  Write a script to find out
-all missing numbers in the range 0..$n where $n is the array size.
+You are given an array of integers.
 
-Example 1
+Write a script to print 1 if there are THREE consecutive odds in the
+given array otherwise print 0.
 
-  Input: @array = (0,1,3)
-  Output: 2
+Example 1
 
-  The array size i.e. total element count is 3, so the range is 0..3.
-  The missing number is 2 in the given array.
+Input: @array = (1,5,3,6)
+Output: 1
 
 Example 2
 
-  Input: @array = (0,1)
-  Output: 2
+Input: @array = (2,6,3,5)
+Output: 0
+
+Example 3
+
+Input: @array = (1,2,3,4)
+Output: 0
 
-  The array size is 2, therefore the range is 0..2.
-  The missing number is 2.
+Example 4
 
-MY NOTES: pretty easy.
+Input: @array = (2,3,5,7)
+Output: 1
+
+MY NOTES: very easy.
 
 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: Penny Piles
+Task 2: Widest Valley
+
+Given a profile as a list of altitudes, return the leftmost widest
+valley. A valley is defined as a subarray of the profile consisting
+of two parts: the first part is non-increasing and the second part is
+non-decreasing. Either part can be empty.
+
+Example 1
+
+Input: 1, 5, 5, 2, 8
+Output: 5, 5, 2, 8
+
+Example 2
+
+Input: 2, 6, 8, 5
+Output: 2, 6, 8
+
+Example 3
 
-You are given an integer, $n > 0.
+Input: 9, 8, 13, 13, 2, 2, 15, 17
+Output: 13, 13, 2, 2, 15, 17
 
-Write a script to determine the number of ways of putting $n pennies in a row of piles of ascending heights from left to right.
-Example
+Example 4
 
-Input: $n = 5
-Output: 7
+Input: 2, 1, 2, 1, 3
+Output: 2, 1, 2
 
-Since $n=5, there are 7 ways of stacking 5 pennies in ascending piles:
+Example 5
 
-    1 1 1 1 1
-    1 1 1 2
-    1 2 2
-    1 1 3
-    2 3
-    1 4
-    5
+Input: 1, 3, 3, 2, 1, 2, 3, 3, 2
+Output: 3, 3, 2, 1, 2, 3, 3
 
-MY NOTES: not quite so easy, but doable.  Sounds recursive to me.
-Let's produce the array of answers too..
+MY NOTES: also quite easy, once we remove the negative "non-increasing"
+language and realise we mean "find the leftmost longest sequence of one
+or more adjacent numbers where initially the numbers go down (or stay
+the same) and then they go up (or stay the same)."
 
 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-202/duncan-c-white/perl/ch-1.pl b/challenge-202/duncan-c-white/perl/ch-1.pl
new file mode 100755
index 0000000000..3536e2a0b7
--- /dev/null
+++ b/challenge-202/duncan-c-white/perl/ch-1.pl
@@ -0,0 +1,93 @@
+#!/usr/bin/perl
+# 
+# Task 1: Consecutive Odds
+# 
+# You are given an array of integers.
+# 
+# Write a script to print 1 if there are THREE consecutive odds in the
+# given array otherwise print 0.
+# 
+# Example 1
+# 
+# Input: @array = (1,5,3,6)
+# Output: 1
+# 
+# Example 2
+# 
+# Input: @array = (2,6,3,5)
+# Output: 0
+# 
+# Example 3
+# 
+# Input: @array = (1,2,3,4)
+# Output: 0
+# 
+# Example 4
+# 
+# Input: @array = (2,3,5,7)
+# Output: 1
+# 
+# MY NOTES: very easy.
+# 
+# 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: 3-consec-odds [--debug] intlist\n"
+	unless GetOptions( "debug"=>\$debug ) && @ARGV>0;
+
+my @list = split( /,/, join(',',@ARGV) );
+
+die "3-consec-odds: need at least 3 ints in list\n" unless @list>2;
+
+=pod
+
+=head2 my $isodd = isodd( $x );
+
+Return 1 iff $x is odd; else 0.
+
+=cut
+sub isodd
+{
+	my( $x ) = @_;
+	return $x % 2 == 1 ? 1 : 0;
+}
+
+
+=pod
+
+=head2 my $has3odds = has3odds( @list );
+
+Return 1 iff @list has 3 consecutive odd numbers; else 0.
+
+=cut
+sub has3odds
+{
+	my( @list ) = @_;
+	my $n = @list;
+
+	for( my $spos=0; $spos<$n-2; $spos++ )
+	{
+		next unless isodd( $list[$spos] );
+		say "debug: found odd element $list[$spos] at pos $spos"
+			if $debug;
+		if( isodd( $list[$spos+1] ) && isodd( $list[$spos+2] ) )
+		{
+			say "debug: found 3 consec odd elements $list[$spos], ".
+			    "$list[$spos+1], $list[$spos+2] starting at ".
+			    "pos $spos" if $debug;
+			return 1;
+		}
+	}
+	return 0;
+}
+
+my $has3odds = has3odds( @list );
+say $has3odds;
diff --git a/challenge-202/duncan-c-white/perl/ch-2.pl b/challenge-202/duncan-c-white/perl/ch-2.pl
new file mode 100755
index 0000000000..4da1d39a78
--- /dev/null
+++ b/challenge-202/duncan-c-white/perl/ch-2.pl
@@ -0,0 +1,103 @@
+#!/usr/bin/perl
+# 
+# Task 2: Widest Valley
+# 
+# Given a profile as a list of altitudes, return the leftmost widest
+# valley. A valley is defined as a subarray of the profile consisting
+# of two parts: the first part is non-increasing and the second part is
+# non-decreasing. Either part can be empty.
+# 
+# Example 1
+# 
+# Input: 1, 5, 5, 2, 8
+# Output: 5, 5, 2, 8
+# 
+# Example 2
+# 
+# Input: 2, 6, 8, 5
+# Output: 2, 6, 8
+# 
+# Example 3
+# 
+# Input: 9, 8, 13, 13, 2, 2, 15, 17
+# Output: 13, 13, 2, 2, 15, 17
+# 
+# Example 4
+# 
+# Input: 2, 1, 2, 1, 3
+# Output: 2, 1, 2
+# 
+# Example 5
+# 
+# Input: 1, 3, 3, 2, 1, 2, 3, 3, 2
+# Output: 3, 3, 2, 1, 2, 3, 3
+# 
+# MY NOTES: also quite easy, once we remove the negative "non-increasing"
+# language and realise we mean "find the leftmost longest sequence of one
+# or more adjacent numbers where initially the numbers go down (or stay
+# the same) and then they go up (or stay the same)."
+# 
+# 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: widest-valley [--debug] intlist\n"
+	unless GetOptions( "debug"=>\$debug ) && @ARGV > 0;
+
+my @list = split( /,/, join(',',@ARGV) );
+
+my $n = @list;
+
+die "widest-valley: need at least 1 int in list\n" unless $n>0;
+
+
+=pod
+
+=head2 my $len = find_valley( $spos, @list );
+
+find the leftmost longest sequence of one or more adjacent numbers
+where initially the numbers go down (or stay the same) and then they
+go up (or stay the same).
+
+=cut
+fun find_valley( $spos, @list )
+{
+	my $n = @list;
+	my $curr = $list[$spos];
+	my $p = $spos+1;
+	for( ; $p<$n && $list[$p] <= $curr; $curr=$list[$p++] )
+	{
+	}
+	for( ; $p<$n && $list[$p] >= $curr; $curr=$list[$p++] )
+	{
+	}
+	my $p1 = $p-1;
+	say "debug: found valley from pos $spos to pos $p1" if $debug;
+	return $p-$spos;
+}
+
+
+my $maxw = 0;
+my $maxw_spos = 0;
+
+for( my $spos=0; $spos<$n; $spos++ )
+{
+	my $w = find_valley( $spos, @list );
+	if( $w > $maxw )
+	{
+		say "debug: found new widest valley starting at $spos: width $w" if $debug;
+		$maxw = $w;
+		$maxw_spos = $spos;
+	}
+}
+
+
+say join( ', ', @list[$maxw_spos..$maxw_spos+$maxw-1] );
diff --git a/challenge-203/duncan-c-white/C/Makefile b/challenge-203/duncan-c-white/C/Makefile
new file mode 100644
index 0000000000..bf2d32d1a1
--- /dev/null
+++ b/challenge-203/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