codeforces #629 D.Carousel

D.Carousel

• 题意：n个数环形排列，让你去染色，唯一的限制是相邻不相同的数要用不同颜色染色。问染色方案。(颜色使用要少)
• 题解: 如果不是环形只需要1，2交错排列就可以满足要求，但是环形会出现 a[n]!=a[1]&&res[n]==res[1]这种情况，我们可以令res[n]=3-res[n],再反向处理一遍，如果还是这种情况，就只能让res[n] = 3了。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<map>
#include<vector>
using namespace std;
typedef long long ll;
const int N = 2e6 + 5;
const int mod = 1e9 + 7;
const double Pi = 3.1415926;
const ll INF = 0x3f3f3f3f;

int T;
int n, k;
int num = 0;
int a[N], res[N], b[N];


int main()
{
	scanf("%d",&T);
	while(T --){
		num = 1;
		scanf("%d",&n);
		for(int i = 1; i <= n; ++ i){
			scanf("%d",&a[i]);
		}
		res[1] = 1;
		for(int i = 2; i <= n; ++ i){
			if(a[i] != a[i - 1]) num = 2, res[i] = 3 - res[i - 1];
			else res[i] = res[i - 1];
		}
		if(a[n] != a[1] && res[n] == res[1]){
			res[n] = 3 - res[n];
			for(int i = n - 1; i >= 1; -- i){
				if(a[i] == a[i + 1]) break;
				else res[i] = 3 - res[i + 1];
			}
			if(res[n] == res[1]){
				num = 3;
				res[n] = 3;
			}
		}
		printf("%d\n",num);
		for(int i = 1; i <= n; ++ i){
			if(i == n) printf("%d\n",res[i]);
			else printf("%d ",res[i]);
		}
	}
	return 0;
	
}