Leetcode-path Sum

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Given a binary tree and a sum, determine if the tree has a root-to-leaf path such this adding up all the values along the Path equals the given sum.

For example:
Given the below binary tree and sum = 22,

              5             /             4   8           /   /           /  4         /  \              7    2      1

Return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

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/** * Definition for binary tree * struct TreeNode {*     int val; *     TreeNode *left; *     TreeNode *right; *     Tre Enode (int x): Val (x), left (null), right (NULL) {} *}; */class Solution {public:    int flag=0;    BOOL Haspathsum (TreeNode *root, int sum) {        if (root==null) return false;                Pathsum (root,0,sum);                if (flag==1)            return true;        else            return false;            }        int Pathsum (TreeNode *root,int res,int sum)    {        if (root==null)  return 0;                res+=root->val;                int l=pathsum (root->left,res,sum);        int r=pathsum (root->right,res,sum);                if ((l+r) ==0&&res==sum)        {            flag=1;        }}            };

Leetcode-path Sum