dij朴素算法总结

原题链接:https://www.acwing.com/problem/content/851/

 

#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn = 510,INF = 0x3f3f3f3f;
int g[maxn][maxn];
int dist[maxn];
bool st[maxn];
int n,m;

int dij(){
    memset(dist,0x3f,sizeof(dist));     
    dist[1] = 0;        //初始化距离
    for(int i = 1;i<n;i++){
        int t = -1;
        for(int j = 1;j<=n;j++)
            if(!st[j]&&(t==-1||dist[t]>dist[j]))
                t = j;
    /* ----------找到集合外距离最小点t----------*/
        st[t] = true;
        for(int j = 1;j<=n;j++)
            dist[j] = min(dist[j],dist[t]+g[t][j]);
    }
    if(dist[n]==0x3f3f3f3f)return -1;
    return dist[n];
}

int main(){
    cin>>n>>m;
    //初始化图
    for(int i = 0;i<=n;i++){
        for(int j = 0;j<=n;j++){
            if(i==j)g[i][j] = 0;
            else g[i][j] = INF;
        }
    }
    //处理重边
    while(m--){
        int a,b,c;
        cin>>a>>b>>c;
        g[a][b] = min(g[a][b],c);
    }
    int t = dij();
    if(t==-1)cout<<-1<<endl;
    else cout<<t<<endl;
    return 0;
}