1040. Longest Symmetric String (25)

题目链接：http://www.patest.cn/contests/pat-a-practise/1040

题目：

1040. Longest Symmetric String (25)

时间限制

400 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

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

分析：

找到一个字符串的最长回文子串，那个时候还不知道kmp,manacher，用比較搓的方法做出来的。

AC代码：

#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string>
using namespace std;
int main(){
 //freopen("F://Temp/input.txt", "r", stdin);
 string str;
 string str_r;
 getline(cin,str);
 str_r = str;
 reverse(str_r.begin(),str_r.end());  //included in the <algorithm>
//先把字符串逆序。然后比較正序和逆序中同样的部分，即为最长回文子串
 int same = 0, sum = 0;
 for (int i = 0; i < str.size(); i++){
  sum = 0;
  for (int j = 0, rj = i; j < str.size() - i; j++,rj ++){
   if (str_r[rj] == str[j]){
    sum++;
    if (sum > same)same = sum;
   }
   else sum = 0;
  }
  sum = 0;
  for (int j = 0, rj = i; j < str.size() - i; j++, rj++){
   if (str_r[j] == str[rj]){
    sum++;
    if (sum > same)same = sum;
   }
   else sum = 0;
  }
 }
 cout << same << endl;
 return 0;
}

截图：

——Apie陈小旭