Merge pull request #7206 from dcw803/master

added my late solutions to challenge 192 (Perl x 2 + C x 2) and..

22 files changed, 1371 insertions, 118 deletions

diff --git a/challenge-192/duncan-c-white/C/Makefile b/challenge-192/duncan-c-white/C/Makefile
new file mode 100644
index 0000000000..0e674ee7dd
--- /dev/null
+++ b/challenge-192/duncan-c-white/C/Makefile
@@ -0,0 +1,19 @@
+# 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 nextintperm.o parseints.o printarray.o
+ch-2.o:	ch-2.c args.h nextintperm.h parseints.h printarray.h
+nextintperm.o:	nextintperm.c nextintperm.h
+parseints.o:	parseints.c args.h parseints.h printarray.h
+printarray.o:	printarray.c
+
diff --git a/challenge-192/duncan-c-white/C/README b/challenge-192/duncan-c-white/C/README
new file mode 100644
index 0000000000..31e5ebdb28
--- /dev/null
+++ b/challenge-192/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 produce near-identical (non-debugging and even debugging) output to my
+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-192/duncan-c-white/C/args.c b/challenge-192/duncan-c-white/C/args.c
new file mode 100644
index 0000000000..d4a2d38b9a
--- /dev/null
+++ b/challenge-192/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-192/duncan-c-white/C/args.h b/challenge-192/duncan-c-white/C/args.h
new file mode 100644
index 0000000000..8844a8f9c4
--- /dev/null
+++ b/challenge-192/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-192/duncan-c-white/C/ch-1.c b/challenge-192/duncan-c-white/C/ch-1.c
new file mode 100644
index 0000000000..d9f6d1cd22
--- /dev/null
+++ b/challenge-192/duncan-c-white/C/ch-1.c
@@ -0,0 +1,37 @@
+//
+// Task 1: Binary Flip
+// 
+// C version.
+// 
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <ctype.h>
+#include <assert.h>
+
+#include "args.h"
+
+
+int main( int argc, char **argv )
+{
+	int n;
+	process_onenumarg_default( "binary-flip", argc, argv, 100, &n );
+
+	if( debug )
+	{
+		printf( "debug: n=%d\n", n );
+	}
+
+	int p = 1;
+	while( p < n )
+	{
+		p *= 2;
+	}
+
+	n = (~ n) & (p-1);
+	printf( "%d\n", n );
+
+	return 0;
+}
diff --git a/challenge-192/duncan-c-white/C/ch-2.c b/challenge-192/duncan-c-white/C/ch-2.c
new file mode 100644
index 0000000000..0b604739e1
--- /dev/null
+++ b/challenge-192/duncan-c-white/C/ch-2.c
@@ -0,0 +1,142 @@
+//
+// Task 2: Equal Distribution
+// 
+// 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 pos = find_pair_diff_gt_1(nel, list[]);
+//	Find the position pos of the first element of the first pair in list
+//	where the absolute difference between list[pos] and list[pos+1] is > 1.
+//	Return -1 if none.
+//
+int find_pair_diff_gt_1( int nel, int *list )
+{
+	for( int pos=0; pos<nel-1; pos++ )
+	{
+		if( abs( list[pos] - list[pos+1] ) > 1 ) return pos;
+	}
+	return -1;
+}
+
+
+//
+// int pos = find_pair_f_lt_s(nel, list[]);
+//	Find the position pos of the first element of a pair in @list
+//	where list[$pos] < list[pos+1].  Return -1 if none.
+//
+int find_pair_f_lt_s( int nel, int *list )
+{
+	for( int pos=0; pos<nel-1; pos++ )
+	{
+		if( list[pos] < list[pos+1] ) return pos;
+	}
+	return -1;
+}
+
+
+int main( int argc, char **argv )
+{
+	int argno = process_flag_n_m_args( "equal-distribution", argc, argv,
+		1, 1000, "intlist" );
+
+	int nel;
+	int *list = parse_int_args( argc, argv, argno, &nel );
+
+	if( nel < 2 )
+	{
+		fprintf( stderr, "equal-distribution: need a list of > 1 elements\n" );
+		exit(1);
+	}
+
+	if( debug )
+	{
+		printf( "debug: initial list: " );
+		print_int_array( 60, nel, list, ',', stdout );
+		putchar( '\n' );
+	}
+
+	int nmoves = 0;
+
+	if( debug )
+	{
+		printf( "starting first pass\n" );
+	}
+
+	// first pass: repeatedly find two adjacent cells whose absolute
+	// difference > 1 and transfer one from the bigger to the smaller.
+	int pos;
+	while( (pos = find_pair_diff_gt_1(nel, list)) != -1 )
+	{
+		if( debug )
+		{
+			printf( "debug: found pos %d, list=", pos );
+			print_int_array( 60, nel, list, ',', stdout );
+			putchar( '\n' );
+		}
+		if( list[pos] < list[pos+1] )
+		{
+			list[pos]++;
+			list[pos+1]--;
+		} else
+		{
+			list[pos]--;
+			list[pos+1]++;
+		}
+		nmoves++;
+	}
+
+	if( debug )
+	{
+		printf( "starting second pass\n" );
+	}
+
+	// second pass: repeatedly find 2 adjacent cells where
+	// firstvalue < secondvalue and transfer one from secondvalue
+	// to firstvalue
+	while( (pos = find_pair_f_lt_s(nel, list)) != -1 )
+	{
+		if( debug )
+		{
+			printf( "debug: found pos %d, list=", pos );
+			print_int_array( 60, nel, list, ',', stdout );
+			putchar( '\n' );
+		}
+		list[pos]++;
+		list[pos+1]--;
+		nmoves++;
+	}
+
+	int firstel = list[0];
+	int nsame = 0;
+	for( pos=0; pos<nel; pos++ )
+	{
+		if( list[pos] == firstel ) nsame++;
+	}
+	bool success = nsame == nel;
+
+	if( debug )
+	{
+		printf( "debug: after %d moves, nsame=%d, success=%d, "
+			"final list=", nmoves, nsame, success );
+		print_int_array( 60, nel, list, ',', stdout );
+		putchar( '\n' );
+	}
+	printf( "%d\n", success ? nmoves : -1 );
+
+	free( list );
+
+	return 0;
+}
diff --git a/challenge-192/duncan-c-white/C/parseints.c b/challenge-192/duncan-c-white/C/parseints.c
new file mode 100644
index 0000000000..0fb9985633
--- /dev/null
+++ b/challenge-192/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-192/duncan-c-white/C/parseints.h b/challenge-192/duncan-c-white/C/parseints.h
new file mode 100644
index 0000000000..da5e145a86
--- /dev/null
+++ b/challenge-192/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-192/duncan-c-white/C/printarray.c b/challenge-192/duncan-c-white/C/printarray.c
new file mode 100644
index 0000000000..ddee597df3
--- /dev/null
+++ b/challenge-192/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-192/duncan-c-white/C/printarray.h b/challenge-192/duncan-c-white/C/printarray.h
new file mode 100644
index 0000000000..40efb83277
--- /dev/null
+++ b/challenge-192/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-192/duncan-c-white/README b/challenge-192/duncan-c-white/README
index d51cea2c1e..4b7a727129 100644
--- a/challenge-192/duncan-c-white/README
+++ b/challenge-192/duncan-c-white/README
@@ -1,89 +1,98 @@
-Task 1: Task 1: Twice Largest
+Task 1: Binary Flip
 
-You are given list of integers, @list.
-
-Write a script to find out whether the largest item in the list is at
-least twice as large as each of the other items.
+You are given a positive integer, $n.
 
+Write a script to find the binary flip.
 Example 1
 
-Input: @list = (1,2,3,4)
-Output: -1
+Input: $n = 5
+Output: 2
 
-The largest in the given list is 4.
-However 4 is not greater than (dcw:OR EQUAL TO) twice remaining element 3:
-2 x 3 >  4
+First find the binary equivalent of the given integer, 101.
+Then flip the binary digits 0 -> 1 and 1 -> 0 and we get 010.
+So Binary 010 => Decimal 2.
 
 Example 2
 
-Input: @list = (1,2,0,5)
-Output: 1
+Input: $n = 4
+Output: 3
 
-The largest in the given list is 5.
-Also 5 is greater than (dcw:OR EQUAL TO) twice of every remaining element.
-1 x 2 <= 5
-2 x 2 <= 5
-0 x 2 <= 5
+Decimal 4 = Binary 100
+Flip 0 -> 1 and 1 -> 0, we get 011.
+Binary 011 = Decimal 3
 
 Example 3
 
-Input: @list = (2,6,3,1)
+Input: $n = 6
 Output: 1
 
-The largest in the given list is 6.
-Also 6 is greater than (dcw:OR EQUAL TO) twice of every remaining element.
-2 x 2 <= 6
-3 x 2 <= 6
-1 x 2 <= 6
-
-Example 4
-
-Input: @list = (4,5,2,3)
-Output: -1
+Decimal 6 = Binary 110
+Flip 0 -> 1 and 1 -> 0, we get 001.
+Binary 001 = Decimal 1
 
-The largest in the given list is 5.
-Also 5 is not greater than (dcw:OR EQUAL TO) twice of every remaining element.
-4 x 2 >  5
-2 x 2 <= 5
-3 x 2 >  5
 
-MY NOTES: very easy, although there's an error in the wording of the examples
-above - to get eg3 to "succeed" (have result 1) it's got to be "max element
-is >= every other element * 2"...
+MY NOTES: very easy.  That's ones complement with a bit of range-fixing!
 
 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: Cute List
+Task 2: Equal Distribution
+
+You are given a list of integers greater than or equal to zero, @list.
+
+Write a script to distribute the number so that each members are same. If you succeed then print the total moves otherwise print -1.
+
+Please follow the rules (as suggested by Neils van Dijke [2022-11-21 13:00]
+
+1) You can only move a value of '1' per move
+2) You are only allowed to move a value of '1' to a direct neighbor/adjacent cell
 
-You are given an integer, 0 < $n <= 15.
 
-Write a script to find the number of orderings of numbers that form a cute list.
+Example 1:
+
+Input: @list = (1, 0, 5)
+Output: 4
+
+Move #1: 1, 1, 4
+(2nd cell gets 1 from the 3rd cell)
+
+Move #2: 1, 2, 3
+(2nd cell gets 1 from the 3rd cell)
+
+Move #3: 2, 1, 3
+(1st cell get 1 from the 2nd cell)
+
+Move #4: 2, 2, 2
+(2nd cell gets 1 from the 3rd cell)
+
+Example 2:
+
+Input: @list = (0, 2, 0)
+Output: -1
+
+It is not possible to make each same.
 
-With an input @list = (1, 2, 3, .. $n) for positive integer $n, an
-ordering of @list is cute if for every entry, indexed with a base index of
-1, either
+Example 3:
 
-1) $list[$i] is evenly divisible by $i
-or
-2) $i is evenly divisible by $list[$i]
+Input: @list = (0, 3, 0)
+Output: 2
 
-Example
+Move #1: 1, 2, 0
+(1st cell gets 1 from the 2nd cell)
 
-Input: $n = 2
-Ouput: 2
+Move #2: 1, 1, 1
+(3rd cell gets 1 from the 2nd cell)
 
-Since $n = 2, the list can be made up of two integers only i.e. 1 and 2.
-Therefore we can have two list i.e. (1,2) and (2,1).
 
-@list = (1,2) is cute since $list[1] = 1 is divisible by 1 and $list[2]
-= 2 is divisible by 2.
+MY NOTES: Hmm..  If I'm understanding that right, it's two passes:
+1. repeatedly find two adjacent cells whose absolute difference > 1
+and transfer one from the bigger cell to the smaller cell.
+2. repeatedly find 2 adjacent cells where firstvalue < secondvalue
+and transfer one from secondvalue to firstvalue
 
-MY NOTES: Hmm.. isn't every number divisible by 1, doesn't that mean that
-the list[1] check is unnecessary?  Looks weird but otherwise reasonably
-straightforward.  Obviously need a "next permutation of the list" iterator,
-reusing the one from Challenge 134, adapted slightly.
+Note also that I'm pretty sure that all lists whose sum is divisible
+by 3 can be balanced, and no list whose sum is NOT divisible by 3 can be.
 
 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-192/duncan-c-white/perl/ch-1.pl b/challenge-192/duncan-c-white/perl/ch-1.pl
new file mode 100755
index 0000000000..c7a408b460
--- /dev/null
+++ b/challenge-192/duncan-c-white/perl/ch-1.pl
@@ -0,0 +1,62 @@
+#!/usr/bin/perl
+# 
+# Task 1: Binary Flip
+# 
+# You are given a positive integer, $n.
+# 
+# Write a script to find the binary flip.
+#
+# Example 1
+#
+# Input: $n = 5
+# Output: 2
+# 
+# First find the binary equivalent of the given integer, 101.
+# Then flip the binary digits 0 -> 1 and 1 -> 0 and we get 010.
+# So Binary 010 => Decimal 2.
+# 
+# Example 2
+# 
+# Input: $n = 4
+# Output: 3
+# 
+# Decimal 4 = Binary 100
+# Flip 0 -> 1 and 1 -> 0, we get 011.
+# Binary 011 = Decimal 3
+# 
+# Example 3
+# 
+# Input: $n = 6
+# Output: 1
+# 
+# Decimal 6 = Binary 110
+# Flip 0 -> 1 and 1 -> 0, we get 001.
+# Binary 001 = Decimal 1
+# 
+# MY NOTES: very easy.  That's ones complement with a bit of range-fixing!
+# 
+# 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: binary-flip [--debug] N\n"
+	unless GetOptions( "debug"=>\$debug ) && @ARGV==1;
+
+my $n = shift;
+$n += 0;
+
+my $p = 1;
+while( $p < $n )
+{
+	$p *= 2;
+}
+
+$n = (~ $n) & ($p-1);
+say "$n";
diff --git a/challenge-192/duncan-c-white/perl/ch-2.pl b/challenge-192/duncan-c-white/perl/ch-2.pl
new file mode 100755
index 0000000000..0d2a76c5fb
--- /dev/null
+++ b/challenge-192/duncan-c-white/perl/ch-2.pl
@@ -0,0 +1,154 @@
+#!/usr/bin/perl
+# 
+# Task 2: Equal Distribution
+# 
+# You are given a list of integers greater than or equal to zero, @list.
+# 
+# Write a script to distribute the number so that each members are
+# same. If you succeed then print the total moves otherwise print -1.
+# 
+# Please follow the rules (as suggested by Neils van Dijke [2022-11-21 13:00]
+# 
+# 1) You can only move a value of '1' per move
+# 2) You are only allowed to move a value of '1' to a direct neighbor/adjacent cell
+# 
+# Example 1:
+# 
+# Input: @list = (1, 0, 5)
+# Output: 4
+# 
+# Move #1: 1, 1, 4
+# (2nd cell gets 1 from the 3rd cell)
+# 
+# Move #2: 1, 2, 3
+# (2nd cell gets 1 from the 3rd cell)
+# 
+# Move #3: 2, 1, 3
+# (1st cell get 1 from the 2nd cell)
+# 
+# Move #4: 2, 2, 2
+# (2nd cell gets 1 from the 3rd cell)
+# 
+# Example 2:
+# 
+# Input: @list = (0, 2, 0)
+# Output: -1
+# 
+# It is not possible to make each same.
+# 
+# Example 3:
+# 
+# Input: @list = (0, 3, 0)
+# Output: 2
+# 
+# Move #1: 1, 2, 0
+# (1st cell gets 1 from the 2nd cell)
+# 
+# Move #2: 1, 1, 1
+# (3rd cell gets 1 from the 2nd cell)
+# 
+# MY NOTES: Hmm..  If I'm understanding that right, it's two passes:
+# 1. repeatedly find two adjacent cells whose absolute difference > 1
+# and transfer one from the bigger cell to the smaller cell.
+# 2. repeatedly find 2 adjacent cells where firstvalue < secondvalue
+# and transfer one from secondvalue to firstvalue
+# 
+# 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: same-list [--debug] intlist\n"
+	unless GetOptions( "debug"=>\$debug ) && @ARGV>0;
+
+my @list = split(/,/, join( ',', @ARGV ));
+
+die "same-list: need a list of > 1 elements\n" if @list<2;
+
+
+=pod
+
+=head2 my $pos = find_pair_diff_gt_1(@list);
+
+Find the position $pos of the first element of the first pair in @list
+where the absolute difference between list[$pos] and list[pos+1] is > 1.
+Return -1 if none.
+
+=cut
+fun find_pair_diff_gt_1( @list )
+{
+	for( my $pos=0; $pos<@list-1; $pos++ )
+	{
+		return $pos if abs( $list[$pos] - $list[$pos+1] ) > 1;
+	}
+	return -1;
+}
+
+
+
+=pod
+
+=head2 my $pos = find_pair_f_lt_s(@list);
+
+Find the position $pos of the first element of a pair in @list
+where list[$pos] < list[pos+1].  Return -1 if none.
+
+=cut
+fun find_pair_f_lt_s( @list )
+{
+	for( my $pos=0; $pos<@list-1; $pos++ )
+	{
+		return $pos if $list[$pos] < $list[$pos+1];
+	}
+	return -1;
+}
+
+
+my $nmoves = 0;
+
+say "starting first pass" if $debug;
+
+# first pass: repeatedly find two adjacent cells whose absolute difference > 1
+# and transfer one from the bigger cell to the smaller cell.
+while( (my $pos = f