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Path Sum

problem

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.

Analysis

using simple deep first search

code

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/*
Definition for binary tree
struct TreeNode {
int val;
TreeNode *left;
TreeNode *right;
TreeNode(int x) : val(x), left(NULL), right(NULL)}
};
*/
class Solution {
public:
bool deep_first_search(TreeNode *node, int sum, int curSum)
{
if (node == NULL)
return false;

if (node->left == NULL && node->right == NULL)
return curSum + node->val == sum;

return deep_first_search(node->left, sum, curSum + node->val) || deep_first_search(node->right, sum, curSum + node->val);
}

bool hasPathSum(TreeNode *root, int sum) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
return deep_first_search(root, sum, 0);
}
};
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