//最大答案数
#define MAX_ANS_NUM 1000000

int comp(const void* a, const void* b) {
    return *((int*)a) - *((int*)b);
}

int** threeSum(int* nums, int numsSize, int* returnSize, int** returnColumnSizes) {
    int** result = (int**)calloc(MAX_ANS_NUM, sizeof(int*));
    *returnColumnSizes = (int*)calloc(MAX_ANS_NUM, sizeof(int));
    *returnSize = 0;
    if (numsSize < 3) return result;
    //先将入参排序
    qsort(nums, numsSize, sizeof(int), comp);
    //排除极端异常情况:
    if (nums[0] + nums[1] + nums[2] > 0) return result; // 最小三个数相加都大于0直接无解
    if (nums[numsSize - 1] + nums[numsSize - 2] + nums[numsSize - 3] < 0) return result; //最大三个数相加都小于0直接无解

    int left, right, anscount;
    anscount = 0;
    for (int i = 0; i < numsSize - 2; i++) 
    {
        if (nums[i] + nums[i + 1] + nums[i + 2])
        {
            if (nums[i] + nums[numsSize - 1] + nums[numsSize -2] < 0) 
            continue; // 剪枝优化无效判断 最小的加上 最大的两个数都小于0继续找下一轮
        }
      
        if (i > 0 && nums[i] == nums[i - 1]) 
        {
            continue; // 重复的判断
        }

        left = i + 1;
        right = numsSize - 1;

        while (left < right) 
        {
            if (nums[left] + nums[i] + nums[right] == 0) 
            {
                result[anscount] = (int*)calloc(3, sizeof(int));
                result[anscount][0] = nums[left];
                result[anscount][1] = nums[i];
                result[anscount][2] = nums[right];
                (*returnColumnSizes)[anscount] = 3;
                anscount++;
                while(left + 1 < right && nums[left] == nums[left + 1]) 
                {
                    left++;
                }
                left++;
                while (left < right - 1 && nums[right] == nums[right - 1]) 
                {
                    right--;
                }
                right--;
            } else if (nums[left] + nums[i] + nums[right] < 0) 
            {
                left++;
            } else if (nums[left] + nums[i] + nums[right] > 0) 
            {
                right--;
            }
        }
    }

    *returnSize = anscount;
    return result;
}