Binary Tree Maximum Path Sum
LeetCode https://leetcode.cn/problems/binary-tree-maximum-path-sum/
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/**
* 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 {
private int max = Integer.MIN_VALUE;
public int maxPathSum(TreeNode root) {
maxPathSumHelper(root);
return max;
}
private int maxPathSumHelper(TreeNode root) {
if (root == null) {
return 0;
}
// Step 1
int left = maxPathSumHelper(root.left);
int right = maxPathSumHelper(root.right);
// Step 2
left = left < 0 ? 0 : left;
right = right < 0 ? 0 : right;
max = Math.max(max, root.val + left + right);
// Step 3
return root.val + Math.max(left, right);
}
}
Complexity
- Time = O(n)
- Space = O(height)
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