zoj 2744 Palindromes (求回文子序列的个数)

链接：zoj 2744

A regular palindrome is a string of numbers or letters that is the same forward as backward. For example, the string "ABCDEDCBA" is a palindrome because it is the same when the string is read from left to right as when the string is read from right to left.

Now give you a string S, you should count how many palindromes in any consecutive substring of S.

Input

There are several test cases in the input. Each case contains a non-empty string which has no more than 5000 characters.

Proceed to the end of file.

Output

A single line with the number of palindrome substrings for each case.

Sample Input

aba
aa

Sample Output

4
3

求回文子序列的个数，如 aba 的回文子序列有 a, b, a, aba.

解析：一个序列，若一个序列中间的两个连续字符或三个连续字符的子序列不回文，则其肯定不回文

代码：

#include<stdio.h>
#include<string.h>
int main()
{
    char s[5005];
    int i,l,r,t,n;
    while(scanf("%s",s)!=EOF){
        t=n=strlen(s);
        for(i=0;i<n;i++){
            l=i;
            r=i+1;
            while(l>=0&&r<n){
                if(s[l--]==s[r++])
                    t++;
                else
                    break;
            }
        }
        for(i=0;i<n;i++){
            l=i;
            r=i+2;
            while(l>=0&&r<n){
                if(s[l--]==s[r++])
                    t++;
                else
                    break;
            }
        }
        printf("%d\n",t);
    }
    return 0;
}