Codeforces Round #411 B.3-palindrome （构造）

CodeForces - 805B 3-palindrome

In the beginning of the new year Keivan decided to reverse his name. He doesn’t like palindromes, so he changed Naviek to Navick.
He is too selfish, so for a given n he wants to obtain a string of n characters, each of which is either ‘a’, ‘b’ or ‘c’, with no palindromes of length 3 appearing in the string as a substring. For example, the strings “abc” and “abca” suit him, while the string “aba” doesn’t. He also want the number of letters ‘c’ in his string to be as little as possible.
Input
The first line contains single integer n (1 ≤ n ≤ 2·105) — the length of the string.
Output
Print the string that satisfies all the constraints.
If there are multiple answers, print any of them.

Example
Input
2
Output
aa
Input
3
Output
bba

题意：只用‘a’’b’ ‘c’构造一个长n的字符串，并且不存在长度为3
的子串为回文串，‘c’要尽量的少。

分析：因为要有长度为3的回文串必定需要b[0]==b[2]
所以只需要每一段都保证是“aab”或者”bba”就可以了
AC代码

#include<stdio.h>char a[5]="aabb";int main(){    int n;    scanf("%d",&n);    int count=0;    for(int i=0;i<n;i++)    {        printf("%c",a[count%4]);        count++;    }    printf("\n");}