路径总和II

class Solution {
public:
    vector<vector<int>> pathSum(TreeNode* root, int targetSum) {
        if(!root)return {};
        vector<vector<int>>ans;
        vector<int>ans1;
        dfs(root,targetSum,ans,ans1);
        return ans;
    }
    void dfs(TreeNode*root,int targetSum,vector<vector<int>>&ans,vector<int>&ans1){
        if(!root->left&&!root->right){
            ans1.push_back(root->val);
            if(root->val==targetSum){
                ans.push_back(ans1);
                return ;
            }else return;
        }
        ans1.push_back(root->val);
        int newVal=targetSum-root->val;
        if(root->left){
            dfs(root->left,newVal,ans,ans1);
            ans1.pop_back();
        }
        if(root->right){
            dfs(root->right,newVal,ans,ans1);
            ans1.pop_back();
        }
    }
};