luogu P3371 单源最短路径 模板 SPFA

Posted 2020-11-01 Misaka_Azusa

题目链接：https://www.luogu.org/problemnew/show/P3371

我永远都喜欢Flyod、dijkstra + heap、SPFA

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <queue>
 4 #include <algorithm>
 5 using namespace std;
 6 const int maxn = 1000000;
 7 const int inf = 0x7fffffff;
 8 int n, m, s, dis[maxn];
 9 bool vis[maxn];
10 struct edge{
11     int to, next, len, from;
12 }e[maxn];
13 int head[maxn], cnt;
14 queue<int> q;
15 void add(int u, int v, int w)
16 {
17     e[++cnt].from = u;
18     e[cnt].to = v;
19     e[cnt].len = w;
20     e[cnt].next = head[u];
21     head[u] = cnt;
22 }
23 int SPFA()
24 {
25     while(!q.empty())
26     {
27         int now = q.front();
28         q.pop();
29         vis[now] = 0;
30         for(int i = head[now]; i ; i = e[i].next)
31         {
32             if(dis[e[i].to] > dis[now]+e[i].len)
33             {
34                 dis[e[i].to] = dis[now]+e[i].len;
35                 if(!vis[e[i].to])
36                 {
37                     vis[vis[e[i].to]] = 1;
38                     q.push(e[i].to);
39                 }
40             }
41         }
42     }
43 }
44 int main()
45 {
46     scanf("%d%d%d",&n,&m,&s);
47     for(int i = 1; i <= n; i++)
48     dis[i] = inf;
49     for(int i = 1; i <= m; i++)
50     {
51         int u,v,w;
52         scanf("%d%d%d",&u,&v,&w);
53         add(u,v,w);
54     }
55     dis[s] = 0;
56     q.push(s);
57     vis[s] = 1;
58     SPFA();
59     for(int i = 1; i <= n; i++)
60     printf("%d ",dis[i]);
61 }