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  • I

      1 //SPFA
      2 #include <iostream>
      3 #include <algorithm>
      4 #include <string>
      5 #include <map>
      6 #include <cstring>
      7 #include <vector>
      8 #include <queue>
      9 using namespace std;
     10 
     11 const int maxn = 50;
     12 const double Start = 100;
     13 
     14 struct node{
     15     int val;
     16     double len;
     17     node(int _val, double _len){
     18         val = _val;
     19         len = _len;
     20     };
     21 };
     22 
     23 map<string ,int>mp;
     24 vector<node>g[maxn];
     25 double d[maxn];
     26 bool vis[maxn];
     27 
     28 #define INF 0xffffff
     29 
     30 void init(int n, int x){
     31     for(int i = 0;i <= n;i++){
     32         d[i] = -INF;
     33         vis[i] = true;
     34     }
     35     d[x] = Start;
     36 }
     37 
     38 queue<int>q;
     39 bool SPFA(int s){
     40     while(!q.empty())
     41         q.pop();
     42     q.push(s);
     43     vis[s] = false;
     44     while(!q.empty()){
     45         int x = q.front();q.pop();
     46         int xl = g[x].size();
     47         for(int i = 0 ;i < xl; i++){
     48             node y = g[x][i];
     49             /*
     50             if(vis[y.val] == false){
     51                 continue;
     52             }
     53             vis[y.val] = true;
     54             */
     55             double k = d[x]*y.len;
     56             if(k > d[y.val]){
     57                 d[y.val] = k;
     58                 q.push(y.val);
     59             }
     60         }
     61         if(d[s] > Start){
     62             return true;
     63         }
     64     }
     65     return false;
     66 }
     67 
     68 int main(){
     69     int n;
     70     int cnt = 0;
     71     while(cin >> n){
     72         mp.clear();
     73         for(int i =0 ;i < maxn;i++){
     74             g[i].clear();
     75         }
     76         cnt++;
     77         if(n == 0)
     78             break;
     79         string s;
     80         for(int i = 1;i <= n;i++){
     81             cin >> s;
     82             mp[s] = i;
     83         }
     84         int m;
     85         cin >> m;
     86         string s1, s2;
     87         double d;
     88         for(int i = 0;i < m;i++){
     89             cin >> s1 >> d >> s2;
     90             int u = mp[s1];
     91             int v = mp[s2];
     92             g[u].push_back(node(v,d));
     93         }
     94 
     95         bool ok = false;
     96         for(int i = 1;i <= n;i++){
     97             init(n, i);
     98             if(SPFA(i)){
     99                 ok = true;
    100                 break;
    101             }
    102         }
    103         cout << "Case " << cnt << ": ";
    104         if(ok){
    105             cout << "Yes" << endl;
    106         }
    107         else{
    108             cout << "No" << endl;
    109         }
    110     }
    111     return 0;
    112 }
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  • 原文地址:https://www.cnblogs.com/ouyang_wsgwz/p/9073847.html
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