LeetCode 298. Binary Tree Longest Consecutive Sequence
原题链接在这里:https://leetcode.com/problems/binary-tree-longest-consecutive-sequence/
题目:
Given a binary tree, find the length of the longest consecutive sequence path.
The path refers to any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The longest consecutive path need to be from parent to child (cannot be the reverse).
For example,
1
\
3
/ \
2 4
\
5
Longest consecutive sequence path is 3-4-5
, so return 3
.
2
\
3
/
2
/
1
Longest consecutive sequence path is 2-3
,not3-2-1
, so return 2
.
题解:
DFS bottom-up方法.
Time Complexity: O(n). Space: O(logn).
AC Java:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
int max = 0;
public int longestConsecutive(TreeNode root) {
dfs(root);
return max;
} private int dfs(TreeNode root){
if(root == null){
return 0;
} int l = dfs(root.left)+1;
int r = dfs(root.right)+1;
if(root.left != null && root.val != root.left.val-1){
l = 1;
} if(root.right != null && root.val != root.right.val-1){
r = 1;
} int curMax = Math.max(l, r);
max = Math.max(max, curMax);
return curMax;
}
}
也可采用top down的方法.
Time Complexity: O(n). Space: O(logn).
AC Java:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public int longestConsecutive(TreeNode root) {
if(root == null){
return 0;
} int [] res = new int[]{0};
dfs(root, root.val, 1, res);
return res[0];
} private void dfs(TreeNode root, int target, int count, int [] res){
if(root == null){
return;
} if(root.val != target+1){
count = 1;
}else{
count++;
} res[0] = Math.max(res[0], count);
dfs(root.left, root.val, count, res);
dfs(root.right, root.val, count, res);
}
}
跟上Binary Tree Longest Consecutive Sequence II.
类似Longest Consecutive Sequence.
LeetCode 298. Binary Tree Longest Consecutive Sequence的更多相关文章
- [LeetCode] 298. Binary Tree Longest Consecutive Sequence 二叉树最长连续序列
Given a binary tree, find the length of the longest consecutive sequence path. The path refers to an ...
- [LeetCode] 549. Binary Tree Longest Consecutive Sequence II 二叉树最长连续序列之 II
Given a binary tree, you need to find the length of Longest Consecutive Path in Binary Tree. Especia ...
- LeetCode 549. Binary Tree Longest Consecutive Sequence II
原题链接在这里:https://leetcode.com/problems/binary-tree-longest-consecutive-sequence-ii/description/ 题目: G ...
- 298. Binary Tree Longest Consecutive Sequence
题目: Given a binary tree, find the length of the longest consecutive sequence path. The path refers t ...
- [LeetCode] 298. Binary Tree Longest Consecutive Sequence_Medium tag: DFS recursive
Given a binary tree, find the length of the longest consecutive sequence path. The path refers to an ...
- 298. Binary Tree Longest Consecutive Sequence最长连续序列
[抄题]: Given a binary tree, find the length of the longest consecutive sequence path. The path refers ...
- [LeetCode] 549. Binary Tree Longest Consecutive Sequence II_ Medium tag: DFS recursive
Given a binary tree, you need to find the length of Longest Consecutive Path in Binary Tree. Especia ...
- [LC] 298. Binary Tree Longest Consecutive Sequence
Given a binary tree, find the length of the longest consecutive sequence path. The path refers to an ...
- [LintCode] 619 Binary Tree Longest Consecutive Sequence III 二叉树最长连续序列 III
Given a k-ary tree, find the length of the longest consecutive sequence path. The path could be star ...
随机推荐
- flex 实现图片播放 方案一 图片全部预加载放内存
这种方案,对于web的应用有局限性,在图片量比较多,比较大的时候,就会爆浏览器异常.一般建议轻量级的采用这种方案. <?xml version="1.0" encoding= ...
- linux 定时任务未执行php脚本
1,对于无法执行php文件,首先你应该考虑的问题是是否php代码有错误,你可以先检查一下你的php代码,或者可以在linux上面执行一下这个文件,看是否能够执行成功:如果成功了,就说明是crontab ...
- css背景透明文字不透明
测试背景透明度为0.3.文字不透明: background-color: #000; /* 一.CSS3的opacity */ opacity: 0.3; /* 兼容浏览器为:firefox,chro ...
- tomcat8配置tomcat-users.xml不生效
一般想进入tomcat管理后台,只要在tomcat-users.xml配置文件中添加一下内容即可 <role rolename="manager-gui"/> < ...
- 移动端tap或touch类型事件的点透问题认识
1.什么是点透? 举例说明:下图B元素是黄色方块,B元素中包含了C元素,C元素是一个a链接,本身自带click事件按,然后又一个半透明的粉色元素A遮盖在B元素上(看图中A元素是覆盖在B元素上的,不然B ...
- 关于在windows命令提示符cmd下运行Java程序的问题
1. win+R出现cmd运行窗口,输入Java源码文件名运行时,错误: 找不到或无法加载主类... 问题背景:我已经配置好了Java环境(安装路径PATH,JAVA_HOME已装好,cmd运行jav ...
- Go Interface概念
简单地说 Interface是一组Method的组合,可以通过Interface来定义对象的一组行为.如果某个对象实现了某个接口的所有方法,就表示它实现了该借口,无需显式地在该类型上添加接口说明.In ...
- 九度oj-题目1103:二次方程计算器
时间限制:1 秒 内存限制:32 兆 特殊判题:否 提交:2799 解决:633 题目描述: 设计一个二次方程计算器 输入: 每个案例是关于x的一个二次方程表达式,为了简单,每个系数都是整数形式. 输 ...
- 山东省第六届ACM省赛 H---Square Number 【思考】
题目描述 In mathematics, a square number is an integer that is the square of an integer. In other words, ...
- iostream与iostream.h的区别
简单来说: .h的是标准C的头文件,没有.h的是标准C++的头文件,两种都是头文件. 造成这两种形式不同的原因,是C++的发展历史决定的,刚才正好有别的人也问这个问题,这里我再回答一下(注意vs200 ...