最短路（SPFA）（模板题）（牛客）

Posted 2021-07-18 行码棋

最短路

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll N = 2e4+5;
const ll M = 2e5+5;
const ll inf = 0x3f3f3f3f;
int n,m;
ll dis[N],vis[N];
struct node
{
    int to,w;
    node(int a,int b)
    {
        to = a,w = b;
    }
};
vector<node>edge[M];
void spfa(int x)
{
    queue<int>q;
    q.push(x);
    vis[x] = true;
    dis[x] = 0;
    while(!q.empty())
    {
        int u = q.front();
        q.pop();
        vis[u] = false;
        for(int i=0;i<edge[u].size();i++)
        {
            int v = edge[u][i].to,w = edge[u][i].w;
            if(dis[v] > dis[u] + w)
            {
                dis[v] = dis[u] + w;
                if(!vis[v])
                {
                    q.push(v);
                    vis[v] = true;
                }
            }
        }
    }
}
int main()
{
    cin>>n>>m;
    for(int i=1;i<=n;i++)
    {
        dis[i] = inf;vis[i]=false;
    }
    while(m--)
    {
        int a,b,c;
        cin>>a>>b>>c;
        edge[a].push_back(node(b,c));
    }
    spfa(1);
    for(int i=2;i<=n;i++)
        cout<<dis[i]<<'\\n';
    return 0;
}