题解 | #密码截取#

从中间扩展

#include <iostream>
#include <valarray>
using namespace std;

int searchd(char *s, char *p, int len){
    int ans = 0;
    while (len--) {
        if(*s == *p){
            ans += 2;    
        }else{
            break;
        }
        s--;
        p++;
    }
    return ans;
}
int main() {
    string input;
    cin >> input;
    int n = input.size();
    int ans = 0;
    for(int i = 1; i < n - 1; ++i){
        if(input[i - 1] == input[i + 1])
        ans = max(ans, 1 + searchd(&input[i - 1], &input[i + 1], min(i, n - i)));
        if(input[i - 1] == input[i])
        ans = max(ans, searchd(&input[i - 1], &input[i], min(i, n - i + 1)));
    }
    cout << ans;
}
// 64 位输出请用 printf("%lld")