最短路扩展——分层图最短路
最短路扩展——分层图最短路
1 #include<algorithm> 2 #include<iostream> 3 #include<cstring> 4 #include<cstdio> 5 #include<vector> 6 #include<queue> 7 using namespace std; 8 typedef long long ll; 9 const int maxv= 4000100; /*记得开(n* k)的2倍*/ 10 const int maxe= 20000100; /*记得开(m* k)的4倍*/ 11 const int inf= 0x3f3f3f3f; 12 13 struct ENode 14 { 15 int to; 16 int w; 17 int Next; 18 }; 19 ENode edegs[maxe]; 20 int Head[maxv], tnt; 21 void init() 22 { 23 memset(Head,-1,sizeof(Head)); 24 tnt = -1; 25 } 26 void Add_ENode(int u,int v,int w) 27 { 28 ++ tnt; 29 edegs[tnt].to = v; 30 edegs[tnt].w = w; 31 edegs[tnt].Next = Head[u]; 32 Head[u] = tnt; 33 ++ tnt; 34 edegs[tnt].to = v; 35 edegs[tnt].w = w; 36 edegs[tnt].Next = Head[u]; 37 Head[u] = tnt; 38 } 39 40 int Dis[maxv]; 41 int vis[maxv]; //判断Dijkstra中是否已经查找过； 42 struct cmpx 43 { 44 bool operator() (int &a, int &b) const 45 { 46 return Dis[a]- Dis[b]> 0; 47 } 48 }; 49 void Dijkstra(int s) 50 { 51 priority_queue<int, vector<int>, cmpx> q; 52 memset(Dis, inf, sizeof(Dis)); 53 memset(vis,0,sizeof(vis)); 54 Dis[s]= 0; 55 q.push(s); 56 57 while (! q.empty()) 58 { 59 int u= q.top(); 60 q.pop(); 61 if (vis[u]) continue; 62 vis[u]= 1; 63 for (int k= Head[u]; k!= -1; k= edegs[k].Next) 64 { 65 int v= edegs[k].to; 66 if (! vis[v]&& Dis[v]> Dis[u]+ edegs[k].w) 67 { 68 Dis[v]= Dis[u]+ edegs[k].w; 69 q.push(v); 70 } 71 } 72 } 73 } 74 75 76 int main() 77 { 78 int n, m, s, t, k; 79 while(~scanf("%d %d %d %d %d", &n, &m, &s, &t, &k)) 80 { 81 init(); 82 while( m--) 83 { 84 int u, v, w; 85 scanf("%d %d %d",&u, &v, &w); 86 for(int i = 0; i <= k; i++) 87 { 88 Add_ENode(u + i * n, v + i * n, w); 89 Add_ENode(v + i * n, u + i * n, w); 90 if(i != k) 91 { 92 Add_ENode(u + i * n, v + (i + 1) * n, 0); 93 Add_ENode(v + i * n, u + (i + 1) * n, 0); 94 } 95 } 96 } 97 Dijkstra(s); 98 int ans = inf; 99 for(int i = 0; i <= k; i++) 100 { 101 ans = min(ans, Dis[t + i * n]); 102 } 103 printf("%d\n",ans); 104 } 105 }
