HDU 1217 Arbitrage SPFA

/*
 * 入隊次數大於n說明一直在轉圈圈了，也就是找到了答案了。這裏SPFA要跑n次，
 * 對於這題蒟蒻認爲不如Floyed寫的快，也可能沒發現好的做法把。
 */
#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e2 + 10;
const int MAXM = 1e4 + 10;

struct E{
    int to, nxt;
    double w;
}edge[MAXM];
int tot;
int head[MAXN];
queue<int> q;
map<string, int> M;
double dis[MAXN];
bool inq[MAXN];
int inqtot[MAXN];
int n, m;

inline void clear(int s){
    while(!q.empty()) q.pop();
    memset(dis, 0, sizeof dis);
    dis[s] = 1;
    memset(inq, false, sizeof inq);
    memset(inqtot, 0, sizeof inqtot);
}

inline void addedge(int u, int v, double w){
    edge[tot].to = v;
    edge[tot].w = w;
    edge[tot].nxt = head[u];
    head[u] = tot++;
}

inline bool SPFA(int s){
    q.push(s);
    inq[s] = true;
    ++inqtot[s];
    while(!q.empty()){
        int id = q.front();
        q.pop();
        inq[id] = false;
        for(int i = head[id]; ~i; i = edge[i].nxt){
            int to = edge[i].to;
            double w = edge[i].w;
            if(dis[id] * w > dis[to]){
                dis[to] = dis[id] * w;
                if(!inq[to]){
                    inq[to] = true;
                    ++inqtot[to];
                    q.push(to);
                    if(inqtot[to] > n) return false;
                }
            }
        }
    }
    return true;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    //cout << setiosflags(ios::fixed) << setprecision(1); //保留小數點後1位
    //cout << setprecision(1); //保留1位有效數字
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);

    int cas = 1;
    while(cin >> n, n){
        tot = 0;
        memset(head, -1, sizeof head);
        M.clear();
        for(int i = 1; i <= n; ++i) {
            string name;
            cin >> name;
            M[name] = i;
        }
        cin >> m;
        for(int i = 1; i <= m; ++i){
            string strs, stre;
            double w;
            cin >> strs >> w >> stre;
            addedge(M[strs], M[stre], w);
        }
        bool findans = false;
        for(int i = 1; i <= n; ++i){
            clear(i);   //別忘記了清空
            if(!SPFA(i)){
                findans = true;
                break;
            }
        }
        if(findans) cout << "Case " << cas++ << ": Yes" << endl;
        else cout << "Case " << cas++ << ": No" << endl;
    }
    return 0;
}