LeetCode Path Sum Java Solutin

最新推荐文章于 2019-05-08 09:23:28 发布

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本文介绍了一个经典的二叉树问题——路径总和问题，并提供了一种递归解决方案。该问题要求判断二叉树中是否存在从根节点到叶子节点的路径，使得路径上的数值之和等于给定的目标值。

Path Sum

Total Accepted: 22467 Total Submissions: 73289 My Submissions

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.

这个题目不难，可以一次通过。

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean hasPathSum(TreeNode root, int sum) {
        
        return pathFind(root, sum);
    }
    public boolean pathFind(TreeNode root, int sum){
        if (root == null){
            return false;
        }
        if (root.left == null && root.right == null){
            if( sum - root.val == 0){
                return true;
            } 
        }
        return (pathFind(root.left, sum - root.val) || pathFind(root.right, sum - root.val));
    }
}