PAT 甲级 1040 Longest Symmetric String (25 分)（字符串最长对称字串,遍历）

1040 Longest Symmetric String (25 分)

 

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

 

题意：

输入一个字符串，求该字符串中最长对称子串的长度。

 

题解：

穷举搜索，既要考虑  baab这种偶数类型的，也要考虑abcba这种技术类型的。

 

AC代码：

#include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<string>
#include<cstring>
using namespace std;
string a;
int main(){
    getline(cin,a);
    int len=a.length();
    int mx=1;
    //先偶数
    int r=0,l=1;
    int k;
    for(r=0;r<len;r++)
    {
        l=r+1;
        k=0;
        int rr=r;
        int ll=l;
        while(rr>=0&&ll<len&&a[rr]==a[ll]){
            k+=2;
            rr--;ll++;
        }
        mx=max(k,mx);
    }
    //再奇数
    for(r=0;r<len;r++)
    {
        l=r+2;
        k=1;
        int rr=r;
        int ll=l;
        while(rr>=0&&ll<len&&a[rr]==a[ll]){
            k+=2;
            rr--;ll++;
        }
        mx=max(k,mx);
    }
    cout<<mx<<endl;
    return 0;
}