1 files changed, 273 insertions, 0 deletions
diff --git a/challenge-209/duncan-c-white/C/ch-2.c b/challenge-209/duncan-c-white/C/ch-2.c
new file mode 100644
index 0000000000..89850b0d53
--- /dev/null
+++ b/challenge-209/duncan-c-white/C/ch-2.c
@@ -0,0 +1,273 @@
+//
+// Task 2: Merge Account
+// 
+// C version.
+// 
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <ctype.h>
+#include <assert.h>
+
+#include "args.h"
+#include "csvsplit.h"
+#include "slist.h"
+
+
+// int nch = countch( target, str );
+//	Count and return the number of occurrences of the target character in str.
+//
+int countch( char target, char *str )
+{
+	int n=0;
+	for( ; *str; str++ )
+	{
+		if( *str == target ) n++;
+	}
+	return n;
+}
+
+
+// extra is really an slist
+static void addemail( char *value, void *s )
+{
+	append_slist( (slist)s, value );
+}
+
+
+// slist emails = splitcommas( emailstr );
+//	form a sorted list of emails from emailstr,
+//	duplicating the emailstr buffer inside the slist
+//	emails will need freeing later
+//
+slist splitcommas( char *emailstr )
+{
+	int n = 1 + countch( ',', emailstr );
+	slist s = make_slist( n, 100 );
+
+	if( debug ) { printf( "emailstr %s, nemails = %d\n", emailstr, n ); }
+	csvForeach( emailstr, &addemail, s );
+	if( s->n != n ) { printf( "warning: sn=%d, n=%d\n", s->n, n ); }
+	assert( s->n == n );
+
+	if( debug )
+	{
+		printf( "debug: slist(emailstr %s) is ", emailstr );
+		print_slist( s, stdout ); putchar( '\n' );
+	}
+
+	return s;
+}
+
+
+// int ne = 0;
+// slist *emails = an slist[argc] array
+// char *name = matchfirstname( &argc, argv, &ne, emails );
+//	Extract the name from arg[0], and then find all matching
+//	arg[i<nargs] (including arg[0] by definition), splitting the
+//	email strings and storing the resultant slist in array emails[ne],
+//	deleting them from arg[] and altering nargs.
+//	Return (a strdup()d copy of) the name common to all;
+//	The caller will need to free name later
+//	
+char *matchfirstname( int *nargs, char **arg, int *nm, slist *emails )
+{
+	char *comma = strchr( arg[0], ',' );
+	assert( comma != NULL );
+	*comma = '\0';
+	char *name = strdup( arg[0] );
+	assert( name != NULL );
+	*comma = ',';			// change arg[0] back
+
+	// now extract name + ',' as the strncmp argument for later
+	char ch = *(comma+1);
+	*(comma+1) = '\0';
+	char *namepluscomma = strdup( arg[0] );
+	assert( namepluscomma != NULL );
+	*(comma+1) = ch;		// change arg[0] back
+
+	int len = 1+comma-arg[0];
+	if( debug )
+	{
+		printf( "debug: arg[0] = %s, name = %s, len inc comma=%d\n",
+			arg[0], name, len );
+	}
+
+	int n = 0;
+	int d = 0;
+	emails[n++] = splitcommas( comma+1 );
+	arg[0] = NULL;
+
+	for( int i=1; i<*nargs; i++ )
+	{
+		if( strncmp(namepluscomma,arg[i],len)==0 )
+		{
+			char *comma2 = arg[i] + len - 1;
+			assert( *comma2 == ',' );
+			emails[n] = splitcommas( comma2+1 );
+			if( debug )
+			{
+				printf( "debug: matched arg[%d] == %s, set emails[n] = ",
+					i, arg[i] );
+				print_slist( emails[n], stdout ); putchar( '\n' );
+			}
+			n++;
+		} else
+		{
+			assert( arg[d] == NULL );
+			arg[d++] = arg[i];
+		}
+		arg[i] = NULL;
+	}
+	free( namepluscomma );
+	*nm = n;
+	*nargs -= n;
+	return name;
+}
+
+
+// dealwith( name, emails, ne );
+//	Given a name and an array emails[ne] of slists from all
+//	original arguments with THE SAME NAME as name,
+//	deal with all output for the given name,
+//	merging the email lists where possible, printing out one or
+//	more name, emails lists as a result.
+//
+void dealwith( char *name, slist *emails, int ne )
+{
+	assert( ne > 0 );
+
+	if( debug )
+	{
+		printf( "debug: merging %d lists\n", ne );
+	}
+
+	while( ne>0 )
+	{
+		slist s1 = emails[0];
+
+		// remove emails[0]
+		for( int i=1; i<ne; i++ )
+		{
+			emails[i-1] = emails[i];
+		}
+		ne--;
+
+		if( debug )
+		{
+			printf( "debug: ne = %d, picked s1 = ", ne );
+			print_slist( s1, stdout ); putchar( '\n' );
+		}
+
+		for( int i=0; i<ne; i++ )
+		{
+			slist s2 = emails[i];
+			if( debug )
+			{
+				printf( "debug: s2 = emails[%d].s = ", i );
+				print_slist( s2, stdout ); putchar( '\n' );
+			}
+			bool any = overlap_slists( s1, s2 );
+			if( debug )
+			{
+				printf( "debug: any overlap between s1 and s2 (emails[%d])? %d\n",
+					i, any );
+			}
+			if( any )
+			{
+				union_slists( s1, s2 );
+				if( debug )
+				{
+					printf( "debug: have altered s1 to " );
+					print_slist( s1, stdout ); putchar( '\n' );
+				}
+
+				// delete emails[i]
+				for( int j=i+1; j<ne; j++ )
+				{
+					emails[j-1] = emails[j];
+				}
+				free_slist( s2 );
+				ne--;
+			}
+		}
+		// found an answer: s1..
+		printf( "[\"%s\"", name );
+		for( int i=0; i<s1->n; i++ )
+		{
+			printf( ", " );
+			printf( "\"%s\"", s1->data[i] );
+		}
+		printf( "], " );
+		free_slist( s1 );
+
+		if( debug )
+		{
+			printf( "debug: remaining emails[] are: " );
+			for( int j=0; j<ne; j++ )
+			{
+				if( j>0 ) putchar('-');
+				print_slist( emails[j], stdout );
+			}
+			putchar( '\n' );
+		}
+	}
+}
+
+
+int main( int argc, char **argv )
+{
+	int argno = process_flag_n_m_args( "merge-accounts", argc, argv,
+		1, 1000, "list(name,emails)" );
+
+	argv += argno;		// reset base, so we now have argv[argc]..
+	argc -= argno;
+
+	for( int i=0; i<argc; i++ )
+	{
+		if( strchr(argv[i],',')==NULL )
+		{
+			fprintf( stderr, "Bad arg %s, no comma found\n", argv[i] );
+			exit(1);
+		}
+	}
+
+	if( debug )
+	{
+		printf( "argc=%d, first arg=%s\n", argc, argv[0] );
+	}
+	printf( "output: [ " );
+
+	while( argc > 0 )
+	{
+		// find a set of email slists with matching names,
+		// using the first argument to pick the name
+		int ne = 0;
+		slist *emails = malloc( argc * sizeof(slist) );
+		assert( emails != NULL );
+		char *name = matchfirstname( &argc, argv, &ne, emails );
+		if( debug )
+		{
+			printf( "debug: ne=%d, ", ne );
+			for( int i=0; i<ne; i++ )
+			{
+				printf( "debug: emails[%d] ", i );
+				print_slist( emails[i], stdout ); putchar( '\n' );
+			}
+			printf( "debug: remaining argc=%d, ", argc );
+			for( int i=0; i<argc; i++ )
+			{
+				printf( "debug: arg %d=%s\n", i, argv[i] );
+			}
+			printf( "debug: need to deal with @emails[%d]\n", ne );
+		}
+		dealwith( name, emails, ne );
+		free( emails );
+		free( name );
+	}
+
+	printf( " ]\n" );
+	return 0;
+}