LeetCode每日一题：二叉树路径和 1

问题描述

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 path5->4->11->2which sum is 22.

问题分析

典型的二叉树递归题，若从根到叶路径之和为sum，返回true

代码实现

public boolean hasPathSum(TreeNode root, int sum) {
        if (root == null) return false;
        if (root.left == null && root.right == null) {
            if (root.val == sum) return true;
            else return false;
        }
        if (root.left != null && hasPathSum(root.left, sum - root.val)) return true;
        if (root.right != null && hasPathSum(root.right, sum - root.val)) return true;
        return false;
    }