[LeetCode 112] Path Sum

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,

      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.

Diffculty
Easy

Similar Problems
[LeetCode 113] Path Sum II Medium [LeetCode 124] Binary Tree Maximum Path Sum Hard [LeetCode 129] Sum Root to Leaf Numbers Medium [LeetCode 437] Path Sum III Easy

Analysis

递归，每递归一层，就把 sum 减去当前根节点的值

Solutions

class Solution {
public:
    bool hasPathSum(TreeNode *root, int sum) {
        if(root == nullptr) return false;
        sum -= root->val;
        if(root->left == nullptr && root->right == nullptr)
            return sum == 0 ? true : false;
        return hasPathSum(root->left, sum) || hasPathSum(root->right, sum);
    }
};