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// 46. Permutations
#include <stdio.h>
#include <stdlib.h>
/*
* given an array 'nums' of distinct integers, return all the possible
* permutations. you can return the answer in any order
*/
void swap(int *p, int *q) {
int tmp = *p;
*p = *q;
*q = tmp;
}
void search(int *nums, int nums_size, int ***arr, int *return_size, int begin,
int end) {
if (begin == end) {
(*return_size)++;
*arr = (int **)realloc(*arr, sizeof(int *) * (*return_size));
(*arr)[*return_size - 1] = (int *)malloc(sizeof(int) * nums_size);
for (int i = 0; i < nums_size; i++)
(*arr)[*return_size - 1][i] = nums[i];
return;
}
for (int i = begin; i <= end; i++) {
swap(nums + begin, nums + i);
search(nums, nums_size, arr, return_size, begin + 1, end);
swap(nums + begin, nums + i);
}
}
int **permute(int *nums, int nums_size, int *return_size,
int **return_col_size) {
*return_size = 0;
int **ans = (int **)malloc(sizeof(int *));
search(nums, nums_size, &ans, return_size, 0, nums_size - 1);
return ans;
}
int main() {
int n1[] = {1, 2, 3}, n2[] = {0, 1}, n3[] = {1};
int **p1 = permute(n1, 3, NULL, NULL);
int **p2 = permute(n2, 2, NULL, NULL);
int **p3 = permute(n3, 1, NULL, NULL);
for (int i = 0; i < 6; i++)
for (int j = 0; j < 3; j++)
printf("%d ", p1[i][j]);
printf("\n");
for (int i = 0; i < 6; i++)
for (int j = 0; j < 3; j++)
printf("%d ", p2[i][j]);
printf("\n");
for (int i = 0; i < 6; i++)
for (int j = 0; j < 3; j++)
printf("%d ", p3[i][j]);
printf("\n");
}
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