题解 | #密码截取#

#include <iostream>
#include <vector>

using namespace std;

/**
 * dp[j][i]表示从j到i的子串是否是回文子串
 */
int maxduichenLen(string str) {
    int n = str.size();
    vector<vector<bool>> dp(n, vector<bool>(n, false));
    int max = 1;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j <= i; ++j) {
            if (i == j) dp[j][i] = true;
            else if (i - j == 1) dp[j][i] = str[i] == str[j];
            else dp[j][i] = (str[i] == str[j] && dp[j + 1][i - 1]);
            if (dp[j][i] && i - j + 1 > max) max = i - j + 1;
        }
    }
    return max;
}

int main() {
    string str;
    while (cin >> str) {
        cout << maxduichenLen(str) << endl;
    }
    return 0;
}