Leetcode: Path Sum

最新推荐文章于 2024-09-06 16:32:48 发布

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本文探讨了如何确定一棵二叉树中是否存在从根节点到叶子节点的路径，使得路径上所有节点值之和等于给定的目标值。通过递归算法实现这一功能，并给出具体示例。

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.

/**
 * 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) {
		// Start typing your Java solution below
		// DO NOT write main() function
		if (root == null)
			return false;
		sum = sum - root.val;
		if (root.left == null && root.right == null && sum == 0)
			return true;
		boolean left = false, right = false;
		if (root.left != null)
			left = hasPathSum(root.left, sum);
		if (root.right != null)
			right = hasPathSum(root.right, sum);
		return left || right;
	}
}