PAT 1040. Longest Symmetric String (25)

1040. Longest Symmetric String (25)

时间限制

400 ms

内存限制

32000 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

---

提交代码

/*
	1.用gets(a); 不能用scanf("%s",a); 因为：要读出完整的字符串直至文件末尾，而不是遇到空格就停止此次读。
	2.二重循环搞定。。
	3.找出一个枢轴，以此为中心检测是否对称chen。分奇对称 和 偶对称 2种情况。
*/
#include
#include
const int MAX=1001;
int main()
{
	int i,j;
	char a[MAX];
	//freopen("G:\\in.txt","r",stdin);
	//freopen("G:\\our.txt","w",stdout);
	while(gets(a)){
		int len=strlen(a),tmp=0,ans=0;
		for(i=0;i=0;j++){
				if(a[i-j]==a[i+j]){  //对称子串有奇数个字符
					tmp=2*j+1;
					if(tmp>ans)
						ans=tmp;
				}else                //此句话起决定性作用，加上就25分，否则只有5分。。。。
					break;
			}
		}
		for(i=0;i=0;j++){
				if(a[i-j+1]==a[i+j]){  //对称子串有偶数个字符
					tmp=2*j;
					if(tmp>ans)
						ans=tmp;
				}else
					break;
			}
		}
		printf("%d\n",ans);
	}
	return 0;
}