【leetcode】78. 子集

int** subsets(int* nums, int numsSize, int* returnSize, int** returnColumnSizes) {
    int** ans = malloc(sizeof(int*) * (1 << numsSize));
    *returnColumnSizes = malloc(sizeof(int) * (1 << numsSize));
    *returnSize = 1 << numsSize;
    int t[numsSize];
    for (int mask = 0; mask < (1 << numsSize); ++mask) {
        int tSize = 0;
        for (int i = 0; i < numsSize; ++i) {
            if (mask & (1 << i)) {
                t[tSize++] = nums[i];
            }
        }
        int* tmp = malloc(sizeof(int) * tSize);
        memcpy(tmp, t, sizeof(int) * tSize);
        (*returnColumnSizes)[mask] = tSize;
        ans[mask] = tmp;
    }
    return ans;
}

void recursion(int* nums,int n, int* returnSize, int* col,int* temp,int cnt,int** arr,int start){
    for(int i=start; i<n; i++){
        temp[cnt]=nums[i];
        arr[(*returnSize)]=(int*)calloc(cnt+1,sizeof(int));
        memcpy(arr[(*returnSize)],temp,(cnt+1)*sizeof(int));
        col[(*returnSize)++]=cnt+1;
        recursion(nums, n, returnSize, col, temp, cnt+1, arr,i+1);
    }
}

int** subsets(int* nums, int numsSize, int* returnSize, int** returnColumnSizes){
    int** arr=(int**)calloc((1<<numsSize),sizeof(int*));
    int temp[100]={0};
    *returnSize=1;
    *returnColumnSizes=(int*)calloc((1<<numsSize),sizeof(int));
    recursion(nums,numsSize,returnSize,*returnColumnSizes,temp,0,arr,0);    
    return arr;
}