#include<stdio.h>
#include<stdlib.h>
 
int permutation(char nchars[], char result[], int count, int max);
void arrayPrint(char a[], int count);
 
int permutation(char nchars[], char result[], int count, int max) {
	int i;
	int j;
	char *remain;
 
	if (count == max) {
		arrayPrint(result, max);
		return EXIT_SUCCESS;
	}
 
	for (i = 0; i < max - count; i++) {		
		remain = calloc(max - count, sizeof(char));
 
		for (j = 0; j < max - count; j++) {
			remain[j] = nchars[j];
		}
 
		result[count] = remain[i];
 
		for (j = i + 1; j < max - count; j++) {
			remain[j - 1] = remain[j];
		}
 
		permutation(remain, result, count + 1, max);
 
		free(remain);
	}
 
	return EXIT_SUCCESS;
}
 
void arrayPrint(char a[], int count) {
	int i;
 
	for (i = 0; i < count; i++) {
		printf("%c", a[i]);
		if (i < count - 1) {
			printf(",");
		} else {
			printf("\n");
		}
	}
}
 
int main(int argc, char *argv[]) {
	char *chars = "abcdefghijklmno";
	char *nchars;
	char *result;
	int n;
	int i;
 
	/* n = atoi(argv[1]); */
	n = 5;
 
	nchars = calloc(n, sizeof(char));
	result = calloc(n, sizeof(char));
 
	for (i = 0; i < n; i++) {
		nchars[i] = chars[i];
	}
 
	permutation(nchars, result, 0, n);
 
	free(result);
	free(nchars);
 
	return EXIT_SUCCESS;
}

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