/
twosatisfiability.cpp
166 lines (145 loc) · 3.2 KB
/
twosatisfiability.cpp
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#ifndef call_from_test
#include <bits/stdc++.h>
using namespace std;
#define call_from_test
#include "stronglyconnectedcomponent.cpp"
#undef call_from_test
#endif
//BEGIN CUT HERE
struct TwoSat{
int n;
SCC scc;
TwoSat(int n):n(n),scc(n*2){}
int negate(int v){return (n+v)%(n*2);}
void add_if(int u,int v){
// u -> v <=> !v -> !u
scc.add_edge(u,v);
scc.add_edge(negate(v),negate(u));
}
void add_or(int u,int v){
// u or v <=> !u -> v
add_if(negate(u),v);
}
void add_nand(int u,int v){
// u nand v <=> u -> !v
add_if(u,negate(v));
}
void set_true(int v){
// v <=> !v -> v
scc.add_edge(negate(v),v);
}
void set_false(int v){
// !v <=> v -> !v
scc.add_edge(v,negate(v));
}
vector<int> build(){
scc.build();
vector<int> res(n);
for(int i=0;i<n;i++){
if(scc[i]==scc[n+i]) return {};
res[i]=scc[i]>scc[n+i];
}
return res;
}
};
//END CUT HERE
#ifndef call_from_test
// test add_if, set_true, set_false
signed CFR441_C(){
int n,m;
scanf("%d %d",&n,&m);
vector<vector<int>> G(n);
for(int i=0;i<n;i++){
int k;
scanf("%d",&k);
G[i].assign(k,0);
for(int &v:G[i]){
scanf("%d",&v);
v--;
}
}
auto NG=[](){puts("No");exit(0);};
TwoSat ts(m);
auto add_edge=
[&](vector<int> &as,vector<int> &bs){
int x=min(as.size(),bs.size());
int i;
for(i=0;i<x;i++){
if(as[i]==bs[i]) continue;
if(as[i]<bs[i]){
ts.add_if(bs[i],as[i]);
}else{
ts.set_true(as[i]);
ts.set_false(bs[i]);
}
break;
}
if((i==x) and (as.size()>bs.size())) NG();
};
for(int i=0;i+1<n;i++)
add_edge(G[i],G[i+1]);
auto vs=ts.build();
if(vs.empty()) NG();
vector<int> ans;
for(int i=0;i<m;i++)
if(vs[i]) ans.emplace_back(i);
puts("Yes");
printf("%d\n",(int)ans.size());
for(int i=0;i<(int)ans.size();i++){
if(i) printf(" ");
printf("%d",ans[i]+1);
}
puts("");
return 0;
}
/*
verified 2019/06/20
http://codeforces.com/contest/875/problem/C
*/
// test add_nand
signed YUKI_470(){
int n;
cin>>n;
vector<string> u(n);
for(int i=0;i<n;i++) cin>>u[i];
auto NO=[](){cout<<"Impossible"<<endl;exit(0);};
if(n>=100) NO();
TwoSat ts(n);
for(int i=0;i<n;i++){
for(int j=0;j<i;j++){
auto &as=u[i];
auto &bs=u[j];
if(as[0]==bs[0] and as[1]==bs[1])
ts.add_nand(i,j);
if(as[0]==bs[1] and as[1]==bs[2])
ts.add_nand(i,ts.negate(j));
if(as[1]==bs[0] and as[2]==bs[1])
ts.add_nand(ts.negate(i),j);
if(as[1]==bs[1] and as[2]==bs[2])
ts.add_nand(ts.negate(i),ts.negate(j));
if(as[0]==bs[0]) ts.add_nand(ts.negate(i),ts.negate(j));
if(as[0]==bs[2]) ts.add_nand(ts.negate(i),j);
if(as[2]==bs[0]) ts.add_nand(i,ts.negate(j));
if(as[2]==bs[2]) ts.add_nand(i,j);
}
}
auto res=ts.build();
if(res.empty()) NO();
for(int i=0;i<n;i++){
if(res[i])
cout<<u[i][0]<<u[i][1]<<" "<<u[i][2]<<endl;
else
cout<<u[i][0]<<" "<<u[i][1]<<u[i][2]<<endl;
}
return 0;
}
/*
verified 2019/10/24
https://yukicoder.me/problems/no/470
*/
signed main(){
//CFR441_C();
//YUKI_470();
return 0;
}
#endif