15. 三数之和c

/**
 * Return an array of arrays of size *returnSize.
 * The sizes of the arrays are returned as *returnColumnSizes array.
 * Note: Both returned array and *columnSizes array must be malloced, assume caller calls free().
 */
int temp[4];

int cmp(const void* a,const void* b){
    int x=*(int*)a;
    int y=*(int*)b;
    if(x>y) return 1;
    return -1;
}

void dfs(int** array,int* nums,int numsSize,int* returnSize,int* column,int index,int sum,int count){
    if(count>3) return ;
    if(index>numsSize) return;
    if(index == numsSize && (count!=3 || sum!=0)) return;
    if(count==3&&sum!=0 ) return ;
    if(count==3 && sum==0){
        column[*returnSize]=3;
        array[*returnSize]=(int*)malloc(sizeof(int)*3);
        for(int i=0;i<3;i++) array[*returnSize][i]=temp[i];
        (*returnSize)++;
        return;
    }
    printf("%d ", index);
    temp[count]=nums[index];
    dfs(array,nums,numsSize,returnSize,column,index+1,sum+nums[index],count+1);
    while(index!=numsSize-1 && nums[index] == nums[index+1]) index++;
    dfs(array,nums,numsSize,returnSize,column,index+1,sum,count);
}

int** threeSum(int* nums, int numsSize, int* returnSize, int** returnColumnSizes) {
    qsort(nums,numsSize,sizeof(int),cmp);
    *returnSize=0;
    int* column=(int*)malloc(sizeof(int)*50000);
    int** array=(int**)malloc(sizeof(int*)*50000);
    dfs(array,nums,numsSize,returnSize,column,0,0,0);
    *returnColumnSizes=column;
    return array;   
}