leetcode 646. Maximum Length of Pair Chain 最长连续元素

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

题意很简单，最直接的方法就是LISS最长递增子序列

建议和leetcode 300. Longest Increasing Subsequence 最长递增子序列LISS 一起学习

代码如下：

#include <iostream>#include <vector>#include <map>#include <set>#include <queue>#include <stack>#include <string>#include <climits>#include <algorithm>#include <sstream>#include <functional>#include <bitset>#include <numeric>#include <cmath>#include <regex>using namespace std;bool cmp(vector<int> a, vector<int> b){    return a[1] < b[1];}class Solution {public:    int findLongestChain(vector<vector<int>>& pairs)     {        sort(pairs.begin(), pairs.end(), cmp);        stack<vector<int>> skt;        for (auto i : pairs)        {            if (skt.empty() == true)                skt.push(i);            else            {                auto top = skt.top();                if (i[0] > top[1])                    skt.push(i);            }        }        return skt.size();    }};