dijsktra算法模板+板子题

Posted 2021-09-04 一只特立独行的猫

#include<iostream>
#include<cstring>

using namespace std;

const int N = 505,M =1e5+5;

int graph[N][N];
int dis[N],vis[N];
int n,m;

void dijkstra(){
    
    memset(dis,0x3f,sizeof dis);
    dis[1]=0;
    //每次更新一个点，贪心的思想
    for(int i=0;i<n;i++){
        int t=-1;
        //寻找到未访问结点最小值的下标
        for(int j=1;j<=n;j++){
            if(vis[j]==0&&(t==-1||dis[j]<dis[t])){
                t=j;
            }
        }
        vis[t]=1;
        //更新
        for(int j=1;j<=n;j++){
            dis[j]=min(dis[j],dis[t]+graph[t][j]);
        }
    }
    if(dis[n]!=0x3f3f3f3f){
        cout<<dis[n]<<endl;
    }else{
        cout<<-1<<endl;
    }
}

int main(){
    cin>>n>>m;
    
    memset(graph,0x3f,sizeof graph);
    
    while(m--){
        int a,b,c;
        cin>>a>>b>>c;
        //解决重边和自环问题
        graph[a][b] = min(graph[a][b],c);
    }
    
    dijkstra();
    return 0;
}