0514 CF#798A Mike and palindrome-优快云博客

本文解析了CodeForces平台上A级难度的一道题目——通过修改一个字符使字符串成为回文串的问题。提供了详细的解题思路及C语言实现代码。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

Mike has a string s consisting of only lowercase English letters. He wants to change exactly one character from the string so that the resulting one is a palindrome.

A palindrome is a string that reads the same backward as forward, for example strings "z", "aaa", "aba", "abccba" are palindromes, but strings "codeforces", "reality", "ab" are not.

Input

The first and single line contains string s (1 ≤ |s| ≤ 15).

Output

Print "YES" (without quotes) if Mike can change exactly one character so that the resulting string is palindrome or "NO" (without quotes) otherwise.

Examples

Input	Output
abccaa	YES
abbcca	NO
abcda	YES

方法：计算前后对称位置处不同的字符有几个。可以查一半，也可以全部查。查后分情况处理。

注意几种情况：

-1：已经对称的奇数串

-2：已经对称的偶数串

-3 :差一位回文的串

源代码：

#include<stdio.h>
#include<string.h>
int main()
{
	char str[20];
	scanf("%s",str);
	int len=strlen(str);
	int i;
	int count=0;
	for(i=0;i<len;i++)
	{
			if(str[i]!=str[len-1-i])	
			count++;
	}
	if(count==2 || (count==0 && len%2==1))
	printf("YES\n");
	else printf("NO\n");
	return 0;
}