C_Competitive_Programming/Werewolf.txt at master · phumipatc/C_Competitive_Programming · GitHub

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#include<bits/stdc++.h>
using namespace std;
int mark[100010];
int in[100010];
int out[100010],ans;
void dfs(int now,int type,int s)
{
	if(mark[now])
		return;
	mark[now] = type;
	in[out[now]]--;
	if(in[out[now]] == 0 || type == 1)
	dfs(out[now],3 - type,s);
}
int main()
{
	int Q;
	scanf("%d",&Q);
	while(Q--)
	{
		int n;
		scanf("%d",&n);
		ans = 0;
		for(int i=1;i<=n;i++)
		{
			scanf("%d",&out[i]);
			in[out[i]]++;
		}
		for(int i=1;i<=n;i++)
		{
			if(!mark[i] && in[i] == 0)
				dfs(i,1,i);
		}
		for(int i=1;i<=n;i++)
		{
			if(!mark[i])
				dfs(i,2,i);
		}
		for(int i=1;i<=n;i++)
		{
			if(mark[i] == 2)
				ans++;
			mark[i] = 0;
			in[i] = 0;
		}
		printf("%d\n",ans);
	}
	return 0;
}