题目链接:https://www.nowcoder.com/practice/12e081cd10ee4794a2bd70c7d68f5507?tpId=37&tags=&title=&diffculty=0&judgeStatus=0&rp=1&ru=/ta/huawei&qru=/ta/huawei/question-ranking
代码:

#include<iostream>
#include<vector>
#include<string>
#include<algorithm>

using namespace std;

int main()
{
    string s;
    while(cin>>s)
    {
        string t(s);
        reverse(t.begin(),t.end());
        int len = t.size();
        int maxlen = 0;
        vector<int> ans(len+1,0);
        vector<vector<int>> dp(len+1,ans);
        for(int i=1;i<len;i++)
        {
            for(int j=1;j<len;j++)
            {
                if(s[i-1]==t[j-1])
                    dp[i][j] = dp[i-1][j-1]+1;
                if(dp[i][j]>maxlen)
                {
                    maxlen = dp[i][j];
                }
            }
        }
        cout<<maxlen<<endl;
    }

    return 0;
}