原题链接在这里:https://leetcode.com/problems/maximum-length-of-pair-chain/description/

题目:

You are given n pairs of numbers. In every pair, the first number is always smaller than the second number.

Now, we define a pair (c, d) can follow another pair (a, b) if and only if b < c. Chain of pairs can be formed in this fashion.

Given a set of pairs, find the length longest chain which can be formed. You needn't use up all the given pairs. You can select pairs in any order.

Example 1:

Input: [[1,2], [2,3], [3,4]]
Output: 2
Explanation: The longest chain is [1,2] -> [3,4]

Note:

  1. The number of given pairs will be in the range [1, 1000].

题解:

Sort pairs first based on first element.

Use dp array, dp[i] means up to i, the maximum length of chain. For all j from 0 to i-1, if pairs[j][1] < pairs[i][0], dp[i] = Math.max(dp[i], dp[j]+1).

Time Complexity: O(n^2). n = pairs.length.

Space: O(n).

AC Java:

 class Solution {
public int findLongestChain(int[][] pairs) {
if(pairs == null || pairs.length == 0){
return 0;
} Arrays.sort(pairs, (a, b)->a[0]==b[0] ? a[1]-b[1] : a[0]-b[0]); int n = pairs.length;
int [] dp = new int[n];
for(int i = 0; i<n; i++){
dp[i] = 1;
for(int j = 0; j<i; j++){
if(pairs[j][1]<pairs[i][0]){
dp[i] = Math.max(dp[i], dp[j]+1);
}
}
} return dp[n-1];
}
}

按照pair的second number 排序pairs. 再iterate pairs, 若当前pair的second number 小于下个pair的first number, 计数res++, 否则跳过下个pair.

Note: 用curEnd把当前的second number标记出来, 不要用pair[i][1], 否则 i 跳动时就不是当前pair的second number了.

Time Complexity: O(nlogn). n = pairs.length.

Space: O(1).

AC Java:

 class Solution {
public int findLongestChain(int[][] pairs) {
Arrays.sort(pairs, (a,b) -> a[1]-b[1]);
int res = 0;
int curEnd = Integer.MIN_VALUE;
for(int [] pair : pairs){
if(pair[0] > curEnd){
res++;
curEnd = pair[1];
}
} return res;
}
}

类似Longest Increasing Subsequence.

LeetCode Maximum Length of Pair Chain的更多相关文章

  1. [LeetCode] Maximum Length of Pair Chain 链对的最大长度

    You are given n pairs of numbers. In every pair, the first number is always smaller than the second ...

  2. LN : leetcode 646 Maximum Length of Pair Chain

    lc 646 Maximum Length of Pair Chain 646 Maximum Length of Pair Chain You are given n pairs of number ...

  3. LC 646. Maximum Length of Pair Chain

    You are given n pairs of numbers. In every pair, the first number is always smaller than the second ...

  4. 【LeetCode】646. Maximum Length of Pair Chain 解题报告(Python)

    作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 贪心算法 日期 题目地址:https://leetc ...

  5. [Swift]LeetCode646. 最长数对链 | Maximum Length of Pair Chain

    You are given n pairs of numbers. In every pair, the first number is always smaller than the second ...

  6. 646. Maximum Length of Pair Chain(medium)

    You are given n pairs of numbers. In every pair, the first number is always smaller than the second ...

  7. 646. Maximum Length of Pair Chain 最长的链条长度

    [抄题]: You are given n pairs of numbers. In every pair, the first number is always smaller than the s ...

  8. 646. Maximum Length of Pair Chain

    You are given n pairs of numbers. In every pair, the first number is always smaller than the second ...

  9. [LeetCode] Maximum Length of Repeated Subarray 最长的重复子数组

    Given two integer arrays A and B, return the maximum length of an subarray that appears in both arra ...

随机推荐

  1. Linux软件包管理 RMP包

    RPM 包的安装虽然很方便和快捷,但是依赖性实在是很麻烦,尤其是库文件依赖,还要去 rpmfind 网站査找库文件到底属于哪个 RPM 包,从而导致 RPM 包的安装非常烦琐.那么,有没有可以自动解决 ...

  2. this 机制的四种规则

    江湖人称,谁调用 this,this 就指向谁. 那么 this 到底绑定或者引用的是哪个对象环境呢,以下便是四种规则 1. 默认绑定全局变量 function fn() { console.log( ...

  3. Linux串口编程(中断方式和select方式)

    Linux下的串口编程,在嵌入式开发中占据着重要的地位,因为很多的嵌入式设备都是通过串口交换数据的.在没有操作系统的我们可以使用UART的中断来出来数据的接受和发送,而在Linux操作系统下,我们也可 ...

  4. MODBUS协议 一种问答方式的通信协议

    源:MODBUS协议 一种问答方式的通信协议 ModBus通信系统协议

  5. P4755 Beautiful Pair

    题目 洛谷 做法 \(i≤x≤j,a[i]<\frac{a[x]}{a[j]}\) 考虑\(a[x]\)的贡献,单调栈预处理\(L,R\)能作为最大值的区间 枚举一端点,仅需另一端点满足条件即可 ...

  6. 20145239杜文超《网络对抗》- Web基础

    20145239杜文超<网络对抗>- Web基础 基础问题回答 1.什么是表单? 表单是一个包含表单元素的区域. 表单元素是允许用户在表单中(比如:文本域.下拉列表.单选框.复选框等等)输 ...

  7. JSP语法及内置对象

    JSP全名为Java Server Pages,中文名叫java服务器页面,其根本是一个简化的Servlet设计,它[1]  是由Sun Microsystems公司倡导.许多公司参与一起建立的一种动 ...

  8. ML 感知机(Perceptrons)

    感知机 Perceptrons 学习Hinton神经网络公开课的学习笔记 https://class.coursera.org/neuralnets-2012-001 1 感知机历史 在19世纪60年 ...

  9. review22

    程序再运行期间,可能需要从外部的存储媒介或其他程序中读入所需要的数据,这就需要使用输入流. 程序可能经常需要获取磁盘上文件的有关信息或在磁盘上创建新的文件等,这就需要学习使用File类. 创建一个Fi ...

  10. dp2--合并石子(一)

    dp2--合并石子(一) 一.心得 二.题目 石子合并(一) 时间限制:1000 ms  |  内存限制:65535 KB 难度:3   描述     有N堆石子排成一排,每堆石子有一定的数量.现要将 ...