Submission #1612028

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Source Code Expand

#include<cstdio>
#include<cstring>
#include<cstdlib>
using namespace std;
const int maxn=100100;
int f1[maxn],f2[maxn];
int cnt1[maxn],cnt2[maxn];
int beg[maxn],nex[maxn<<1],tto[maxn<<1],e;
void putin(int s,int t){
	tto[++e]=t;
	nex[e]=beg[s];
	beg[s]=e;
}
int val[maxn];
struct node{
	int s,t;
}w[maxn<<1];
int num;
void setgraph(){
	memset(beg,0,sizeof(beg));
	e=0;
}
int dfs(int u){
	int v=-1,t;
	if(cnt1[u]&1) v=u;
	for(int i=beg[u];i;i=nex[i]){
		t=dfs(tto[i]);
		if(v==-1) v=t;
		else w[++num]=(node){v,t},v=-1;
	}
	if(v==-1){
		printf("IMPOSSIBLE\n");
		exit(0);
	}
	return v;
}
void color(int u,int v){
	val[u]=v;
	for(int i=beg[u];i;i=nex[i]){
		if(val[tto[i]]){
			if(val[tto[i]]==val[u]){
				printf("IMPOSSIBLE\n");
				exit(0);
			}
		}
		else
			color(tto[i],-v);
	}
}
int main(){
//	freopen("F.in","r",stdin);
//	freopen("F.out","w",stdout);
	int n,rt;
	scanf("%d",&n);
	for(int i=1;i<=n;i++){
		scanf("%d",&f1[i]);
		if(f1[i]>0) cnt1[f1[i]]++;
	}
	for(int i=1;i<=n;i++){
		scanf("%d",&f2[i]);
		if(f2[i]>0) cnt2[f2[i]]++;
	}
	for(int i=1;i<=n;i++)
	{
		cnt1[i]=!(cnt1[i]&1);
		cnt2[i]=!(cnt2[i]&1);
		if(cnt1[i]!=cnt2[i]){
			printf("IMPOSSIBLE\n");
			return 0;
		}
	}

	setgraph();
	for(int i=1;i<=n;i++)
	{
		if(f1[i]>0)
			putin(f1[i],i);
		else
			rt=i;
	}
	dfs(rt);

	setgraph();
	for(int i=1;i<=n;i++)
	{
		if(f2[i]>0)
			putin(f2[i],i);
		else
			rt=i;
	}
	dfs(rt);
	
	setgraph();
	for(int i=1;i<=num;i++)
	{
		putin(w[i].s,w[i].t);
		putin(w[i].t,w[i].s);
	}

	for(int i=1;i<=n;i++)
		if(!val[i]&&(cnt1[i]&1))
			color(i,1);

	printf("POSSIBLE\n");
	for(int i=1;i<=n;i++)
		printf("%d ",val[i]);
	printf("\n");
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:54:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
                ^
./Main.cpp:56:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&f1[i]);
                     ^
./Main.cpp:60:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&f2[i]);
                     ^

Judge Result