#include <stdio.h>
#include <string.h>
#include <stdlib.h>
// Swap two chars
void swap(char *a, char *b) {
char tmp = *a;
*a = *b;
*b = tmp;
}
// Print array of chars
void printArray(const char *arr, int size) {
for (int i = 0; i < size; i++) {
printf("%c ", arr[i]);
}
printf("\n");
}
// Recursive function to generate permutations
void permute(char *arr, int l, int r) {
if (l == r) {
printArray(arr, r + 1);
return;
}
for (int i = l; i <= r; i++) {
swap(&arr[l], &arr[i]);
permute(arr, l + 1, r);
swap(&arr[l], &arr[i]); // backtrack
}
}
// Generate all combinations using bitmask
void generateCombinations(const char *arr, int size) {
for (int mask = 1; mask < (1 << size); mask++) {
for (int i = 0; i < size; i++) {
if (mask & (1 << i)) {
printf("%c ", arr[i]);
}
}
printf("\n");
}
}
int main() {
char input[] = "abc";
int size = strlen(input);
printf("All permutations:\n");
permute(input, 0, size - 1);
printf("\nAll combinations:\n");
generateCombinations(input, size);
return 0;
}
/*
run:
All permutations:
a b c
a c b
b a c
b c a
c b a
c a b
All combinations:
a
b
a b
c
a c
b c
a b c
*/
