dp 将复杂度降到n平方
#include<iostream>
#include<vector>
#include<queue>
#include<stack>
#include<string>
#include<math.h>
#include<algorithm>
#include<map>
#include<cstring>
#include<set>
using namespace std;
bool dp[100][100];
int main()
{
string s;
cin >> s;
int maxn = s.size();
for (int i = 0; i < maxn; i++)
{
dp[i][i] = true;
}
int max = 1;
for (int j = 1; j < maxn; j++)
{
for (int i = 0; i < maxn - 1&&i<j; i++)
{
if (s[i] != s[j])
{
dp[i][j] = false;
}
else
{
if (j - i < 3)
{
dp[i][j] = true;
}
else
{
dp[i][j] = dp[i + 1][j - 1];
}
}
if (dp[i][j] && j - i + 1 > max)
{
max = j - i + 1;
}
}
}
cout << max << endl;
}