toj3859. Letter Order

简单拓扑排序

#include <map>
#include <set>
#include <stack>
#include <queue>
#include <cmath>
#include <ctime>
#include <vector>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std;
#define INF 0x3f3f3f3f
#define inf -0x3f3f3f3f
#define lson k<<1, L, mid
#define rson k<<1|1, mid+1, R
#define mem0(a) memset(a,0,sizeof(a))
#define mem1(a) memset(a,-1,sizeof(a))
#define mem(a, b) memset(a, b, sizeof(a))
typedef long long ll;
const int maxn=100;
vector<int>G[maxn];
int degree[maxn];
int vis[maxn];
int cun[maxn];
int m;

int topcode(){
    priority_queue<int,vector<int>,greater<int> >Q;
    int num=26;
    for(int i=0;i<=25;i++){
        if(degree[i]==0)
            Q.push(i);
    }
    int case1=0;
    while(!Q.empty()){
        case1++;
        int u=Q.top();
        Q.pop();
        num--;
        cun[case1]=u;
        for(int i=0;i<G[u].size();i++){
            degree[G[u][i]]--;
            if(degree[G[u][i]]==0)
                Q.push(G[u][i]);
        }   
    }
    if(num>0)
        return 0;
    else
        return 1;
}


int main(){
     int t;
     int n;
     while(scanf("%d",&n)!=EOF){
        mem0(degree);
        mem0(vis);
        for(int i=0;i<=100;i++)
            G[i].clear();
        char x,y;
        for(int i=0;i<n;i++){
            cin>>x>>y;
            int a=x-'A';
            int b=y-'A';
            G[a].push_back(b);
            degree[b]++;
        }
        int flag=topcode();
        if(flag==0)
            cout<<"Stupid Ant!"<<endl;
        else{
            char c[100];
            for(int i=1;i<=26;i++)
                c[i]='A'+cun[i];
            for(int i=1;i<=26;i++)
                cout<<c[i];
            cout<<endl;
        }
     }
     return 0;
}