string permutation

permutation.c

#ifdef SHELL
gcc -ansi -g $0 && ./a.out
exit 0
#endif

#include <stdio.h>
#include <string.h>

void permutation (char * prefix, char * str) {
	int n = strlen(str);

	if ( n == 0 ) {  /* If we don't have any char left in the string
		The prefix is the output */
		printf("%s\n", prefix);
	} else {
		int i;
		for ( i = 0; i < n; i++ ) {
			char newprefix[strlen(prefix)+2];
			/* The new prefix has a car of the previous string */
			sprintf(newprefix, "%c%s", str[i], prefix);

			/* And we will remove a char of the previous string */
			char newstr[strlen(str)];
			newstr[0] = '\0';
			if ( i > 0 ) {
				sprintf(newstr,"%.*s", i, str);
			}
			if (i < n-1) {
				sprintf(& newstr[strlen(newstr)], "%.*s", n-i, & str[i+1]);
			}

			/* We apply the permutation */
			permutation(newprefix, newstr);
		}
	}
}

void main() {
	permutation("", "Daddy");
}