[模板]单源最短路径

Posted 2020-10-24 ycrpro

 

https://www.luogu.org/problemnew/show/P3371

 1 #include <cstring>
 2 #include <cstdio>
 3 #include <iostream>
 4 #include <queue>
 5 #define lop(i,a,b) for(register int i=a;i<=b;++i)
 6 const int N = 10010, M = 500010, inf = 2147483647;
 7 using namespace std;
 8 const int bufsize = 500000;
 9 char buf[bufsize], *p1, *p2;
10 #define getchar() (p1==p2&&(p2=(p1=buf)+fread(buf,1,bufsize,stdin),p1==p2)?EOF:*p1++)
11 
12 inline int read(){
13     register int c = getchar(), f = 1, x = 0;
14     while (!isdigit(c)){if (c == ‘-‘)f = -1; c = getchar();}
15     while (isdigit(c)){x = x * 10 + c - ‘0‘; c = getchar();}
16     return x * f;
17 }
18 int head[N], dis[N], tot, n, m, s, t;bool vis[N];
19 struct Edge{int v, w, next;}G[M];
20 struct Node{
21     int u, w;
22     bool operator<(const Node & rhs) const{
23         return w > rhs.w;
24     }
25 };
26 
27 inline void addedge(int u, int v, int w){
28     G[++tot].v=v;G[tot].w=w;G[tot].next=head[u];head[u]=tot;
29 }
30 inline void Dijkstra(int s){
31     //memset(dis,127,sizeof(dis));
32     priority_queue<Node> q;
33     lop(i,1,n)dis[i] = inf;
34     dis[s] = 0;
35     q.push((Node){s,dis[s]});
36     while(!q.empty()){
37         Node x = q.top();q.pop();
38         int u = x.u;
39         if (vis[u]) continue;
40         for(int i = head[u];i;i = G[i].next){
41             int v = G[i].v,w = G[i].w;
42             if (dis[u] + w < dis[v]){
43                 dis[v] = dis[u] + w;
44                 q.push((Node){v, dis[v]});
45             }
46         }
47         vis[u] = 1;
48     }
49 }
50 
51 int main(void){
52     n = read(), m = read(), s = read();
53     lop(i,1,m){
54         int u = read(), v = read(), w = read();
55         addedge(u, v, w);
56     }
57     Dijkstra(s);
58     lop(i,1,n)printf("%d ", dis[i]);
59     return 0;
60 }

Dijkstra

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <vector>
 4 #include <queue>
 5 #include <cstring>
 6 using namespace std;
 7 const int N=10005;
 8 const int M=500005;
 9 const int inf=0x7f7f7f7f;
10 struct Node{
11     int v, w;
12 };
13 inline Node Make_Node(int v, int w){
14     Node a; a.v = v; a.w = w;
15     return a;
16 }
17 vector<Node> g[N];
18 int dis[N],n,tot,head[N],inq[N],m,s;
19 queue<int> q;
20 
21 inline int read(){
22     int f=1,x=0;char ch;
23     do{ch=getchar();if(ch==‘-‘)f=-1;}while(ch<‘0‘||ch>‘9‘);
24     do{x=x*10+ch-‘0‘;ch=getchar();}while(ch>=‘0‘&&ch<=‘9‘);
25     return f*x;
26 }
27 inline void addedge(int u,int v,int w){
28    g[u].push_back(Make_Node(v, w));
29 }
30 inline void spfa(int s){
31     memset(dis,127,sizeof(dis));dis[s]=0;
32     q.push(s);inq[s]=1;
33     while(!q.empty()){
34         /*int u=q.front();q.pop();inq[u]=0;
35         for(int i=head[u];i;i=G[i].next){
36             int v=G[i].v;
37             if(dis[u]+G[i].w<dis[v]){
38                dis[v]=dis[u]+G[i].w;
39           //  dis[v] = min(dis[v], dis[u] + G[i].w);
40                 if(!inq[v])q.push(v),inq[v]=1;
41             }
42         }*/
43         int u = q.front();q.pop();inq[u] = 0;
44         for(int i = 0; i < g[u].size(); ++i){
45             int v = g[u][i].v, w = g[u][i].w;
46             if (dis[u]+w< dis[v]){
47                 dis[v] = dis[u] + w;
48                 if (!inq[v])q.push(v),inq[v] = 1;
49             }
50         }
51     }
52 }
53 int main(){
54     n=read();m=read();s=read();
55     for(int i=1;i<=m;i++){
56         int u=read(),v=read(),w=read();
57         addedge(u,v,w);
58     }
59     spfa(s);
60     for(int i=1;i<=n;i++)printf("%d%c",dis[i]==inf?2147483647:dis[i],i==n?‘\n‘:‘ ‘);
61     return 0;
62 }

SPFA