题目：

题解：

int* temp;
int tempSize;

int** ans;
int* ansColumnSize;
int ansSize;

int accumulate(int* tmp, int tmpSize) {
    int ret = 0;
    for (int i = 0; i < tmpSize; ++i) {
        ret += tmp[i];
    }
    return ret;
}

void dfs(int cur, int n, int k, int sum) {
    if (tempSize + (n - cur + 1) < k || tempSize > k) {
        return;
    }
    if (tempSize == k && accumulate(temp, tempSize) == sum) {
        int* tmp = malloc(sizeof(int) * tempSize);
        memcpy(tmp, temp, sizeof(int) * tempSize);
        ans[ansSize] = tmp;
        ansColumnSize[ansSize++] = tempSize;
        return;
    }
    temp[tempSize++] = cur;
    dfs(cur + 1, n, k, sum);
    tempSize--;
    dfs(cur + 1, n, k, sum);
}

int** combinationSum3(int k, int n, int* returnSize, int** returnColumnSizes) {
    ansColumnSize = malloc(sizeof(int) * 2001);
    temp = malloc(sizeof(int) * 2001);
    ans = malloc(sizeof(int*) * 2001);
    ansSize = tempSize = 0;

    dfs(1, 9, k, n);
    *returnSize = ansSize;
    *returnColumnSizes = ansColumnSize;
    return ans;
}