LeetCode 491. 递增子序列

class Solution {
public:
    vector<vector<int>> ans;
    vector<int> path;
    void dfs(vector<int> nums,int idx)//选择path的下一个数填什么，从下标idx开始选
    {
        if(path.size()>=2)   ans.push_back(path);
        if(idx==nums.size())
            return;
        set<int> s;
        for(int i=idx;i<nums.size();i++)
            if(path.empty()||nums[i]>=path.back())
            {
                if(s.count(nums[i]))    continue;
                s.insert(nums[i]);
                path.push_back(nums[i]);
                dfs(nums,i+1);
                path.pop_back();
            }
    }
    vector<vector<int>> findSubsequences(vector<int>& nums) {
        dfs(nums,0);
        return ans;
    }
};