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

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

题目地址：https://leetcode.com/problems/maximum-length-of-pair-chain/description/
题目描述：

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

Example1:

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

  又是dp，继续加深理解。

分析：[1,2],[2,3],[3,4]dp[i] : max length of chaindp[i] = Math.max(dp[i],dp[j]+1) if(dp[j][1] < dp[i][0] ) 0<=j<i

Solution:

class Solution {    public int findLongestChain(int[][] pairs) {        Arrays.sort(pairs,(a,b) -> a[0] - b[0]);        int[] dp = new int[pairs.length];        for(int i=0 ; i<pairs.length; 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[pairs.length-1];    }}

Date：2017年11月15日