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

本題大意

輸入一個字串，求該字串中最長對稱子串的長度。

分析

本題考查字串處理的知識，掌握string的一些常用函式(e.g. substr，獲取字串子串)解此題不難。

 #include <iostream>
 #include <algorithm>
 using namespace
 
 std;
 int main(){
    string s;
    int maxlen=0;
    getline(cin,s);
    for(int i=0;i<s.size();i++){
        for(int j=i+1;j<=s.size();j++){
            string s1=s.substr(i,j),s2=s1;
            reverse(s2.begin(),s2.end());
            if(s2==s1 && maxlen<s1.size()) maxlen=s1.size
 
();
        }
    }
    printf("%d",maxlen);
    return 0;
 }