LeetCode 646 Maximum Length of Pair Chain (贪心)

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

Note:

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

题目链接：https://leetcode.com/problems/maximum-length-of-pair-chain/description/

题目分析：经典的贪心问题，按照第二个数字对数组排序，然后按题意尽可能多的取即可，原因很简单，要保证后面尽可能多的取，那么前面也应该尽可能早的结束

class Solution {        public int findLongestChain(int[][] pairs) {        int n = pairs.length;        if (n == 1) {            return 1;        }        Arrays.sort(pairs, new Comparator<int[]>() {            public int compare(int[] o1, int[] o2) {                return o1[1] - o2[1];            }        });        int ans = 1, i = 1, r = pairs[0][1];        while (i < n) {            while (i < n && pairs[i][0] <= r) {                i ++;            }            if (i == n) {                break;            }            r = pairs[i][1];            ans ++;        }        return ans;    }}