HDU 1811 并查集

题意：

思路：topo+并查集

#include <cstdio>
#include <vector>
#include <algorithm>
#include <queue>
#include <iostream>
using namespace std;
vector<int > web[100010];
int p[100010],n,m,sum,f[100010],A[100010],B[100010];
char C[100010];
bool ok;
int find(int x) {return p[x] == x ? x : p[x] = find(p[x]);}
void order(){
    queue<int> q;
    for ( int i = 0 ; i < n ; ++i)
        if ( f[i] == 0 && find(i) == i )
            q.push(i);
    while(!q.empty()){
        if ( q.size() > 1) ok=true;///否则说明信息不完全
        int cur = q.front();
        q.pop();
        sum--;
        for(int i = 0 ; i < web[cur].size() ; ++i)
        {
            if(--f[web[cur][i]]==0)
                q.push(web[cur][i]);
        }
    }
    return ;
}
int main(){
    while (scanf("%d %d",&n,&m) != EOF){
        ok = false ;sum = n;
        for (int i = 0 ;i <= n;++i){
            p[i] = i;
            web[i].clear();
            f[i] = 0 ;
        }
        for (int i = 0 ;i < m; ++i){
            scanf("%d %c %d",&A[i],&C[i],&B[i]);
            int x = find(A[i]),y = find(B[i]);
            if (C[i] == '='){
                if (x != y){
                    p[y] = x;
                    sum--;
                }
            }
        }
        for (int i = 0 ;i < m;++i){
            if (C[i] == '=') continue;
            int x = find(A[i]);
            int y = find(B[i]);
            if (C[i] == '>'){
                web[x].push_back(y);
                f[y]++;
            }
            else {
                web[y].push_back(x);
                f[x]++;
            }
        }
        order();
        if (sum > 0)  printf("CONFLICT
");
        else if (ok)  printf("UNCERTAIN
");
        else printf("OK
");
    }
    return 0;
}