题目：

题解：

int** ans;
int ansSize;
int* temp;
int tempSize;

void dfs(int cur, int last, int* nums, int numsSize, int** returnColumnSizes) {
    if (cur == numsSize) {
        if (tempSize >= 2) {
            ans[ansSize] = malloc(sizeof(int) * tempSize);
            memcpy(ans[ansSize], temp, sizeof(int) * tempSize);
            (*returnColumnSizes)[ansSize++] = tempSize;
        }
        return;
    }
    if (nums[cur] >= last) {
        temp[tempSize++] = nums[cur];
        dfs(cur + 1, nums[cur], nums, numsSize, returnColumnSizes);
        tempSize--;
    }
    if (nums[cur] != last) {
        dfs(cur + 1, last, nums, numsSize, returnColumnSizes);
    }
}

int** findSubsequences(int* nums, int numsSize, int* returnSize, int** returnColumnSizes) {
    ans = malloc(sizeof(int*) * 32768);
    *returnColumnSizes = malloc(sizeof(int*) * 32768);
    temp = malloc(sizeof(int) * numsSize);
    ansSize = tempSize = 0;
    dfs(0, INT_MIN, nums, numsSize, returnColumnSizes);
    *returnSize = ansSize;
    return ans;
}