Luo Gu P1339 [USACO09OCT] heat wave Heat Wave (shortest)

Ok...

 

Topic link: https: //www.luogu.org/problem/P1339

 

This question is not the shortest path problem of water in the water naked here ... using dijkstra

 

But he himself entered into a pit -

　　Because there may be no road between some cities, it was just initialized to 0, and should be initialized to 0x3f3f, so that there is no road between the two cities ...

 

AC Code:

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<algorithm>
 4 #include<cstring>
 5 
 6 using namespace std;
 7 const int inf = 0x3f3f;
 8 int n, c, ts, te, dis[2505], vis[2505], g[5005][5005];
 9 
10 inline void dijkstra(int x){
11     for(int i = 1; i <= n; i++) dis[i] = (i == x ? 0 : inf);
12     for(int i = 1; i <= n; i++){
13         int t = 0, y = inf;
14         for(int j = 1; j <= n; j++) if(!vis[j] && dis[j] <= y) y = dis[t = j]; 
15         vis[t] = 1;
16         for(int j = 1; j <= n; j++) dis[j] = min(dis[j], dis[t] + g[t][j]);
17     }
18 }
19     
20 
21 int main(){
22     memset(g, 0x3f3f, sizeof(g));//初始化！！
23     scanf("%d%d%d%d", &n, &c, &ts, &te);
24     for(int i = 1; i <= c; i++){
25         int u, v, w;
26         scanf("%d%d%d", &u, &v, &w);
27         g[u][v] = g[v][u] = w;
28     }
29     dijkstra(ts);
30     printf("%d", Dis [te]);
31      return  0 ;
32 }

AC Code