题解 | #密码截取#

#include <iostream>
#include <string>
#include <vector>
using namespace std;

int main(int argc, char* argv[]){
    string str;
    getline(cin, str);

    vector<vector<bool>> dp(str.size(), vector<bool>(str.size(), false));
    for(int i = 0; i < str.size(); ++i){
        dp[i][i] = true;
    }
    int maxlen = 1;
    for(int i = str.size() - 2; i >= 0; --i){
        for(int j = i + 1; j < str.size(); ++j){
            if(j - i == 1){
                dp[i][j] = (str[i] == str[j]);
            }
            else{
                dp[i][j] = (str[i] == str[j] && dp[i+1][j-1]);
            }
            if(dp[i][j] && j-i+1 > maxlen){
                maxlen = j-i+1;
            }
        }
    }
    cout << maxlen << endl;

    return 0;
}