算法训练第八周

最新推荐文章于 2025-12-17 23:19:09 发布

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#算法

二、路径总和

在这里插入图片描述

1.深度优先搜索

使用递归的方式遍历二叉树，判断当前节点是否为叶子节点，如果是叶子节点，判断路径和是否等于目标和。如果不是叶子节点，则递归遍历左右子树，直到找到叶子节点或者遍历完整个二叉树。具体代码如下：

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public boolean hasPathSum(TreeNode root, int targetSum) {
        if(root == null) {
            return false;
        }
        int sum = 0;
        return process(root,targetSum,sum);
    }
    public boolean process(TreeNode head,int targetSum,int sum) {
        if(head == null) {
            return false; 
        }
        sum += head.val;
        if(head.right == null && head.left == null && sum != targetSum) {
            return false;
        }
        if(head.right == null && head.left == null && sum == targetSum) {
            return true;
        }
        return process(head.left,targetSum,sum) || process(head.right,targetSum,sum);
    }
}