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Cod sursa(job #654418)
#include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;
#define MAXN 200010
int I[MAXN], minI[MAXN], index, S[MAXN], inS[MAXN], t;
int scc_cnt, node_to_scc[MAXN], scc_in_deg[MAXN];
vector<int> G[MAXN], scc_G[MAXN], scc_list[MAXN];
inline int non(int x, int N){
return (x > N)? x-N: x+N;
}
inline int rescale(int x, int N){
return (x < 0)? -x+N: x;
}
void scc(int n){
I[n]=minI[n]=++index;
S[++t]=n; inS[n]=1;
vector<int>::iterator ii;
for(ii=G[n].begin(); ii!=G[n].end(); ii++){
if(I[*ii] == -1){
scc(*ii);
minI[n]=min(minI[n], minI[*ii]);
}
else if(inS[*ii])
minI[n]=min(minI[n], minI[*ii]);
}
if(I[n] == minI[n]){
scc_cnt++;
do {
node_to_scc[S[t]]=scc_cnt;
scc_list[scc_cnt].push_back(S[t]);
inS[S[t]]=0;
} while(S[t--] != n);
}
}
int main(){
freopen("2sat.in", "r", stdin);
freopen("2sat.out", "w", stdout);
int N, M, i, a, b, l, r, n, impossible, aux;
static int Q[MAXN], value[MAXN];
vector<int>::iterator ii;
scanf("%d%d", &N, &M);
for(i=0; i<M; i++){
scanf("%d%d", &a, &b);
a=rescale(a, N); b=rescale(b, N);
G[non(a, N)].push_back(b);
G[non(b, N)].push_back(a);
}
for(i=1; i<=(N<<1); i++){
I[i]=-1;
value[i]=-1;
}
index=-1; t=-1;
for(i=1; i<=(N<<1); i++)
if(I[i] == -1)
scc(i);
impossible=0;
for(i=1; i<=N; i++)
if(node_to_scc[i] == node_to_scc[i+N])
impossible=1;
if(!impossible){
for(i=1; i<=(N<<1); i++)
for(ii=G[i].begin(); ii!=G[i].end(); ii++)
if(node_to_scc[i] != node_to_scc[*ii]){
scc_G[node_to_scc[i]].push_back(node_to_scc[*ii]);
scc_in_deg[node_to_scc[*ii]]++;
}
r=-1;
for(i=1; i<=scc_cnt; i++)
if(scc_in_deg[i] == 0)
Q[++r]=i;
for(l=0; l<=r; l++){
n=Q[l];
for(ii=scc_list[n].begin(); ii!=scc_list[n].end(); ii++){
aux=(*ii > N)? *ii-N: *ii;
if(value[aux] == -1)
value[aux]=(*ii > N)? 1: 0;
}
for(ii=scc_G[n].begin(); ii!=scc_G[n].end(); ii++){
scc_in_deg[*ii]--;
if(scc_in_deg[*ii] == 0)
Q[++r]=*ii;
}
}
for(i=1; i<=N; i++)
printf("%d ", value[i]);
printf("\n");
}
else
printf("-1\n");
return 0;
}