题解 | #密码截取#

#include <algorithm>
#include <bits/stdc++.h>
using namespace std;
int main() {
    string line;
    getline(cin, line);
    vector<vector<bool>> dp(line.size(), vector<bool>(line.size(), false)) ;
    int max1 = 1;
    for(int right = 0; right < line.size(); ++right) {
        for(int left = right; left >= 0; --left) {
            if(line[left] == line[right]) {
                if(right - left <= 2 || dp[left + 1][right - 1]) dp[left][right] = true;
                if(dp[left][right]) 
                    max1 = max(max1, right - left + 1);
            }
        }
    }
    cout << max1;
}