Leetcode 124. Binary Tree Maximum Path Sum

最新推荐文章于 2024-03-25 21:39:45 发布

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本文探讨了使用深度优先搜索(DFS)算法解决路径求和问题的方法。通过递归方式，设定基线规则和递归规则，巧妙利用整型数组传递参数，避免Java的值传递限制。代码示例清晰展示了如何找到二叉树中最大的路径和。

Problem:

在这里插入图片描述

Analysis:

In this problem, I gonna use DFS to solve it. By using recursion, we should set up the base rule and recursive rule.
there is a small trick in this problem, we should pass the int[] not a int, since java pass value. we need an array to wrap the integer.

Code:

public int maxPathSum(TreeNode root) {
        
        if (root == null){
            return 0;
        }
        
        int[] k = new int[]{Integer.MIN_VALUE};
        dfs(root, k);
        
        return k[0];
    }
    
    private int dfs(TreeNode root, int[] k){
        // base leaf node, --> null?
        
        // recursion rull
        int left = root.left == null? 0 : Math.max(dfs(root.left, k), 0);
        int right = root.right == null? 0: Math.max(dfs(root.right, k), 0);
        int cur = root.val + left + right;
        k[0] = Math.max(k[0], cur);
        return root.val + Math.max(right, left);
       
    }