题解 | #密码截取#

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

int main(){
    string s;
    while(cin >> s){
        int maxlen = 0;
        for(int i = 1; i < s.length(); i++){ //每个点都可以为中心
            //计算以i-1和i为中心的偶数长度的回文子串长度
            int low = i - 1, high = i;
            while(low >= 0 && high < s.length() && s[low] == s[high]){ //中心两边必须都相同
                low--;  
                high++;
            }
            maxlen = max(maxlen, high - low - 1); 
            //计算以i为中心的奇数长度的回文子串长度
            low = i - 1, high = i + 1;
            while(low >= 0 && high < s.length() && s[low] == s[high]){ //中心两边必须都相同
                low--;
                high++;
            }
            maxlen = max(maxlen, high - low - 1);
        }
        cout << maxlen << endl;
    }
    return 0;
}