Path Sum (Easy)

Description

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.

1
2
3
4
5
6
7
8
9
10
For example:
Given the below binary tree and sum = 22,
              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

简单递归

My Solution

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
//C++
/**
 * 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 hasPathSum(TreeNode *root, int sum)
    {
        if(root==NULL)
            return false;
        if(root->left==NULL&&root->right==NULL){
            if(root->val == sum)
                return true;
            return false;
        }
        if(root->left)
        {
            if(hasPathSum(root->left,sum-root->val))
                return true;
        }
        if(root->right){
            if(hasPathSum(root->right,sum-root->val))
                return true;
        }
        return false;
    }
};