1040 Longest Symmetric String (25分)

Posted 2020-12-23 qinmin

Given a string, you are supposed to output the length of the longest symmetric sub-string. For example, given Is PAT&TAP symmetric?, the longest symmetric sub-string is s PAT&TAP s, hence you must output 11.

Input Specification:

Each input file contains one test case which gives a non-empty string of length no more than 1000.

Output Specification:

For each test case, simply print the maximum length in a line.

Sample Input:

Is PAT&TAP symmetric?

Sample Output:

11

#include <iostream>
#include<cstring>
#include<string>
#include<cstdio>
using namespace std;

int main()
{
    string str;
    getline(cin,str);
    int size = str.size();
    int ans = 1;
    for(int i=0;i<size;i++)//左边开始的指针
    {
        for(int j=size-1;j>=i;j--)//右边开始的指针
        {
            if(str[i]==str[j])//左右相等就继续往里走
            {


            bool flag = true;//假设符合
           int t1 = i;
           int t2 = j;

            while(t1<=t2)//判断i,j之间是否全部对称
            {
                t1++;
                t2--;
                if(str[t1]!=str[t2])//不相等就退出
                {
                    flag = false;
                    break;
                }
            }
            if(flag )//i，j间全部对称就更新
                ans = max(ans,j-i+1);
            }
        }
    }

    cout<<ans;
    return 0;
}