66 lines
1.4 KiB
C++
66 lines
1.4 KiB
C++
#include<cstdio>
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#include<vector>
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#include<stack>
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using namespace std;
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template<typename T> inline void read(T& t)
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{
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t=0; bool f=false; char ch;
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while(ch=getchar(),!((ch>='0'&&ch<='9')||ch=='-'));
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if(ch=='-') f=true,ch=getchar();
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t=ch-'0';
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while(ch=getchar(),ch>='0'&&ch<='9') t=t*10+ch-'0';
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if(f) t=-t;
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}
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template<typename T,typename... Args> inline void read(T& t,Args&... args) { read(t); read(args...); }
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const int maxn=1e6+7;
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int n,m,x,xval,y,yval;
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vector<int> G[maxn*2];
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int id[maxn][70];
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int dfn[maxn*2],lowlink[maxn*2],sccno[maxn*2],dfs_cnt,scc_cnt;
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stack<int> stk;
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void dfs(int u)
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{
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dfn[u]=lowlink[u]=++dfs_cnt;
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stk.push(u);
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for(int i=0;i<G[u].size();i++)
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{
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int v=G[u][i];
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if(!dfn[v])
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{
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dfs(v);
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lowlink[u]=min(lowlink[u],lowlink[v]);
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}
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else if(!sccno[v]) lowlink[u]=min(lowlink[u],dfn[v]);
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}
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if(lowlink[u]==dfn[u])
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{
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scc_cnt++;
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while(true)
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{
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int x=stk.top(); stk.pop();
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sccno[x]=scc_cnt;
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if(x==u) break;
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}
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}
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}
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int main()
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{
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#ifdef local
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freopen("pro.in","r",stdin);
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#endif
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read(n,m);
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while(m-->0)
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{
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read(x,xval,y,yval);
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x--; y--;
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x=x*2+xval; y=y*2+yval;
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G[x^1].push_back(y);
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G[y^1].push_back(x);
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}
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for(int i=0;i<2*n;i++) if(!dfn[i]) dfs(i);
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for(int i=0;i<2*n;i+=2) if(sccno[i]==sccno[i+1]) { puts("IMPOSSIBLE"); return 0; }
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puts("POSSIBLE");
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for(int i=0;i<n;i++) printf("%d ",sccno[i*2]>sccno[i*2+1]); puts("");
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return 0;
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}
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