113-Path-Sum-II.cpp

class Solution {
public:
// same as preOrder.....some additional condn are added
    void helper(TreeNode* root, vector<int> v ,vector<vector<int>> &ans, int sum){
        if(root==NULL) return;
        if(root->left==NULL && root->right==NULL){
            if(root->val == sum){
                v.push_back(root->val);
                ans.push_back(v);
            }
            return;
        }
        v.push_back(root->val);
        helper(root->left , v , ans, sum-(root->val)); 
        helper(root->right , v , ans, sum-(root->val));
        // here targetSum is reduced and when it reaches 
        // the leaf sum will be(rest) value of leaf node
        
    }
    vector<vector<int>> pathSum(TreeNode* root, int targetSum) {
        vector<vector<int>> ans;
        vector<int> v;
        helper(root, v, ans, targetSum);
        return ans;  
    }
};