PAT A1040. Longest Symmetric String (25)

1. Longest Symmetric String (25)

時間限制
400 ms
內存限制
65536 kB
代碼長度限制
16000 B
判題程序
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

#include<cstdio>
#include<cstring>
using namespace std;
const int maxn=1010;
char s[maxn];
int dp[maxn][maxn];
int ans=1;
int main(){
    gets(s);
    int len=strlen(s);
    for(int i=0;i<len;i++){
        dp[i][i]=1;
        if(i<len-1){
            if(s[i]==s[i+1]){
                dp[i][i+1]=1;
                ans=2;
            }
        }
    }
    for(int L=3;L<=len;L++){
        for(int i=0;i+L-1<len;i++){
            int j=i+L-1;
            if(s[i]==s[j]&&dp[i+1][j-1]==1){
                dp[i][j]=1;
                ans=L;
            }
        }
    }
    printf("%d\n",ans);
    return 0;
}