hdu 1811 Rank of Tetris

并查集+拓扑排序

#include<iostream>#include<vector>#include<queue>#define maxn 20005using namespace std;int n,m;vector<int>g[maxn];int head[maxn];struct stu{int a,b;string c;};stu mapp[maxn];int f[maxn];void init(){for(int i=0;i<maxn;i++) f[i]=i,g[i].clear(),head[i]=0;}int dfs(int x){if(f[x]!=x) f[x]=dfs(f[x]);return f[x];}void merge(int x,int y){int rx=dfs(x);int ry=dfs(y);if(rx!=ry) f[ry]=rx;}int add(int x,int y){g[x].push_back(y);head[y]++;}void topo(){queue<int>root;int flag=0;for(int i=0;i<n;i++){if(f[i]==i&&!head[i]) root.push(dfs(i));}int re=0;while(root.size()){int x=root.front();root.pop();if(root.size()!=0) flag=1;re++;head[x]--;for(int i=0;i<g[x].size();i++)          {              head[g[x][i]]--;              if(!head[g[x][i]]) root.push(g[x][i]);          } }for(int i=0;i<n;i++) if(f[i]!=i) re++;if(re!=n){cout<<"CONFLICT"<<endl;return;}if(flag==1){cout<<"UNCERTAIN"<<endl;return;} cout<<"OK"<<endl;}int main(){cin.sync_with_stdio(false);while(cin>>n>>m){init();int flag=0;for(int i=0;i<m;i++){cin>>mapp[i].a>>mapp[i].c>>mapp[i].b;if(mapp[i].c=="=") merge(mapp[i].a,mapp[i].b);}for(int i=0;i<m;i++){mapp[i].a=dfs(mapp[i].a);mapp[i].b=dfs(mapp[i].b);if(mapp[i].c=="=") continue;if(mapp[i].b==mapp[i].a) flag=1;if(mapp[i].c=="<") add(mapp[i].a,mapp[i].b);else add(mapp[i].b,mapp[i].a);}if(flag) cout<<"CONFLICT"<<endl;else topo();}return 0;}