Path Sum

Desicription

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

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

1
2
3
4
5
6
7
5
/ \
4 8
/ / \
11 13 4
/ \ \
7 2 1

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

Solution

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/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
private:
bool flag = 0;
void searchTree(TreeNode* root, int sum, const int& target) {
if(root == NULL || flag)
return ;
if(root->left == NULL && root->right == NULL)
if(sum + root->val == target)
flag = 1;
searchTree(root->left, sum + root->val, target);
searchTree(root->right, sum + root->val, target);
}
public:
bool hasPathSum(TreeNode* root, int sum) {
if(root == NULL)
return 0;
searchTree(root, 0, sum);
return flag;
}
};