洛谷P1396 营救 图论
洛谷P1396 营救
图论 dijkstra + 堆优化
1 #include <cstdio> 2 #include <cstring> 3 #include <cmath> 4 #include <cstdlib> 5 #include <string> 6 #include <algorithm> 7 #include <iomanip> 8 #include <iostream> 9 #include <queue> 10 #include <vector> 11 using namespace std ; 12 13 const int maxn = 10011 ,maxm = 20011,inf = 1e9 ; 14 int n,m,s,t,cnt,x,y,v,ans ; 15 struct node{ 16 int to,pre,val ; 17 }; 18 node e[2*maxm] ; 19 int dist[maxn],vis[maxn],head[maxn] ; 20 21 struct data{ 22 int dist,pos ; 23 }; 24 25 struct cmp{ 26 bool operator() (data a,data b) 27 { 28 return a.dist > b.dist ; 29 } 30 }; 31 priority_queue <data,vector<data>,cmp> Q ; 32 33 inline void addedge(int x,int y,int v) 34 { 35 e[++cnt] = (node){ y,head[x],v } ; 36 head[x] = cnt ; 37 } 38 39 inline int dij(int s,int t) 40 { 41 int u,v ; 42 for(int i=1;i<=n;i++) dist[ i ] = inf ; 43 for(int i=1;i<=n;i++) vis[ i ] = false ; 44 data p ; 45 dist[ s ] = 0 ; 46 p = (data){ 0,s } ; 47 Q.push(p) ; 48 while(!Q.empty()) 49 { 50 p = Q.top() ; 51 Q.pop() ; 52 //while(!Q.empty()&&vis[Q.top().pos]) Q.pop() ; 53 if(vis[p.pos]) continue ; 54 u = p.pos ; 55 vis[ u ] = 1 ; 56 for(int i=head[ u ];i;i = e[ i ].pre) 57 { 58 v = e[ i ].to ; 59 dist[ v ] = min( max(e[ i ].val,dist[u]) , dist[ v ] ) ; 60 p = (data){ dist[v],v } ; 61 Q.push(p) ; 62 } 63 } 64 return dist[ t ] ; 65 } 66 67 int main() 68 { 69 scanf("%d%d%d%d",&n,&m,&s,&t) ; 70 for(int i=1;i<=m;i++) 71 { 72 scanf("%d%d%d",&x,&y,&v) ; 73 addedge(x,y,v) ; 74 addedge(y,x,v) ; 75 } 76 77 ans = dij(s,t) ; 78 printf("%d\n",ans) ; 79 return 0 ; 80 }
