leetcode寻找最大长度的连续数对

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本文介绍了一种寻找最长数对链的算法实现。给定一系列数对，每个数对内的第一个数字总是小于第二个数字。文章详细解释了如何确定一个数对能跟随另一个数对的条件，并展示了如何通过特定的排序和动态规划方法找到最长数对链的长度。

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https://leetcode.com/problems/maximum-length-of-pair-chain/description/
Maximum Length of Pair Chain
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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].

class Solution {
private:
    static bool cmp(const vector<int> &a,const vector<int> &b)
    {
        return a[0]<b[0];
    }

public:
    int findLongestChain(vector<vector<int>>& pairs) 
    {
        int ans=0;
        int dp[1000]={0};
        dp[pairs.size()-1]=1;
        std::sort(pairs.begin(), pairs.end(), cmp);

        // for(int i=0;i<=pairs.size()-1;i++)
        // {
        //     cout<<pairs[i][0]<<","<<pairs[i][1]<<endl;
        // }
        for(int i=pairs.size()-1; i>=0; i--)
        {
            int maxnum=0;
            for(int j=i; j<=pairs.size()-1; j++)
            {
                if(pairs[i][1] < pairs[j][0] && dp[j] > maxnum)
                {
                    maxnum = dp[j];
                }
            }
            dp[i]=maxnum+1;
            if(ans<dp[i])
            {
                ans=dp[i];
            }
        }
        return ans;
    }
};