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// 15. 3Sum
#include "leetcode.h"
/*
* given an integer array 'nums', return all the triplets '[nums[i], nums[j],
* nums[k]]' such that 'i != j', 'i != k', 'j != k', and 'nums[i] + nums[j] +
* nums[k] == 0'. notice that the solution set must not contain duplicate
* triplets
*/
int cmp(const void *a, const void *b) { return *((int *)a) - *((int *)b); }
int **threeSum(int *nums, int numsSize, int *returnSize,
int **returnColumnSizes) {
qsort(nums, numsSize, sizeof(int), cmp);
(*returnSize) = 0;
(*returnColumnSizes) = (int *)malloc(sizeof(int) * numsSize * numsSize);
int **ans = (int **)malloc(numsSize * numsSize * sizeof(int *));
for (int i = 0; i < numsSize - 2; i++)
if (!i || nums[i] != nums[i - 1]) {
int l = i + 1, r = numsSize - 1;
while (l < r) {
if (nums[i] + nums[l] + nums[r] < 0)
l++;
else if (nums[i] + nums[l] + nums[r] > 0)
r--;
else {
ans[(*returnSize)] = (int *)malloc(3 * sizeof(int));
(*returnColumnSizes)[(*returnSize)] = 3;
ans[(*returnSize)][0] = nums[i];
ans[(*returnSize)][1] = nums[l];
ans[(*returnSize)][2] = nums[r];
(*returnSize)++;
l++;
while (l < r && nums[l] == nums[l - 1])
l++;
}
}
}
return ans;
}
int main() {
int n1[] = {-1, 0, 1, 2, -1, -4}, rs1, *rcs1;
int n2[] = {0, 1, 1}, rs2, *rcs2;
int n3[] = {0, 0, 0}, rs3, *rcs3;
int **ts1 = threeSum(n1, ARRAY_SIZE(n1), &rs1, &rcs1);
int **ts2 = threeSum(n2, ARRAY_SIZE(n2), &rs2, &rcs2);
int **ts3 = threeSum(n3, ARRAY_SIZE(n3), &rs3, &rcs3);
for (int i = 0; i < rs1; i++) {
for (int j = 0; j < *rcs1; j++)
printf("%d ", ts1[i][j]); // expect: [[-1,-1,2],[-1,0,1]]
printf("\n");
}
printf("\n");
for (int i = 0; i < rs2; i++) {
for (int j = 0; j < *rcs2; j++)
printf("%d ", ts2[i][j]); // expect: null
printf("\n");
}
printf("\n");
for (int i = 0; i < rs3; i++) {
for (int j = 0; j < *rcs3; j++)
printf("%d ", ts3[i][j]); // expect: [[0,0,0]]
printf("\n");
}
printf("\n");
for (int i = 0; i < rs1; i++)
free(ts1[i]);
free(ts1);
for (int i = 0; i < rs2; i++)
free(ts2[i]);
free(ts2);
for (int i = 0; i < rs3; i++)
free(ts3[i]);
free(ts3);
}
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