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// 491. Non-decreasing Subsequences
#include <stdio.h>
#include <stdlib.h>
/*
* given: integer array 'nums'
* return: all possible different non-decreasing subsequences
* of given array with at least two elements. return value can be in any order
*
* returns an array of arrays of size '*returnSize'
* sizes of the arrays are returned as '*returnColumnSizes' array
* note: both returned array and '*columnSizes' array must be malloc'd
* (assume caller free()'s)
*/
int **ans, ansTop, *path, pathTop, *len;
int findUsed(int *uset, int usetSize, int key) {
for (int i = 0; i < usetSize; i++)
if (uset[i] == key)
return 1;
return 0;
}
void backtracking(int *nums, int numsSize, int startIdx) {
if (pathTop >= 2) {
int *tmp = malloc(sizeof(int) * pathTop);
for (int i = 0; i < pathTop; i++)
tmp[i] = path[i];
len[ansTop] = pathTop;
ans[ansTop++] = tmp;
}
int *uset = malloc(sizeof(int) * numsSize), usetTop = 0;
for (int i = startIdx; i < numsSize; i++) {
if (pathTop > 0 && nums[i] < path[pathTop - 1] ||
findUsed(uset, usetTop, nums[i]))
continue;
uset[usetTop++] = nums[i];
path[pathTop++] = nums[i];
backtracking(nums, numsSize, i + 1);
pathTop--;
}
}
int **findSubsequences(int *nums, int numsSize, int *returnSize,
int **returnColumnSizes) {
ans = malloc(sizeof(int *) * 40000);
path = malloc(sizeof(int) * numsSize);
len = malloc(sizeof(int) * 40000);
pathTop = ansTop = 0;
backtracking(nums, numsSize, 0);
*returnSize = ansTop;
*returnColumnSizes = malloc(sizeof(int) * ansTop);
for (int i = 0; i < ansTop; i++)
(*returnColumnSizes)[i] = len[i];
return ans;
}
int main() { int nums1[] = {4, 6, 7, 7}, nums2[] = {4, 4, 3, 2, 1}; }
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