leetcode 113. 路径总和 II

递归到叶子才将tans推进去ret
ret.push_back(tans);

class Solution {
public:
    vector<vector<int>> pathSum(TreeNode* root, int sum) {
        vector<vector<int>> ret;
        findw(root,sum,{},ret);
        return ret;
    }
    void findw(TreeNode* root, int sum,vector<int> tans,vector<vector<int>>&ret){
        if(!root){
            return;
        }
        if(root->val == sum && !root->left && !root->right){
            tans.push_back(root->val);
            ret.push_back(tans);
        }else{
            tans.push_back(root->val);
            if(root->left){
                findw(root->left,sum - root->val,tans,ret);
            }
            if(root->right){
                findw(root->right,sum - root->val,tans,ret);
            }
        }
    }

};