A

#include<bits/stdc++.h>
using namespace std;
const int N=5e5+10,maxx= 2147483647;
typedef pair<int,int>pii;
int h[N],ne[N],e[N],w[N],idx;
int dist[N];
bool st[N];
int n,m,s;
void add(int a,int b,int c)
{
    e[idx]=b,w[idx]=c,ne[idx]=h[a],h[a]=idx++;
}
void dijistra()
{
    memset(dist,0x3f,sizeof dist);
    dist[s]=0;
    priority_queue<pii,vector<pii>,greater<pii>>q;
    q.push({0,s});
    while(!q.empty())
    {
        pii k=q.top();
        q.pop();
        int v=k.second,d=k.first;
        if(st[v])continue;
        st[v]=true;
        for(int i=h[v];i!=-1;i=ne[i])
        {
            int j=e[i];
            if(dist[j]>d+w[i])
            {
                dist[j]=d+w[i];
                q.push({dist[j],j});
            }
        }
    }
}
int main()
{
    cin>>n>>m>>s;
    memset(h,-1,sizeof h);
    while(m--)
    {
        int a,b,c;
        cin>>a>>b>>c;
        add(a,b,c);
    }
    dijistra();
    for(int i = 1; i <= n; i++)
    {
            if(dist[i] == 0x3f3f3f3f)
            {
                cout << maxx <<" ";
            }
            else
            {
                cout << dist[i] <<" ";
            }
    }
    return 0;
}

B

堆优化

#include<bits/stdc++.h>
using namespace std;
const int maxx = 2e5 + 100;
int h[maxx], ne[maxx], idx, e[maxx],w[maxx],dist[maxx];
int n, m, s;
bool st[maxx];
typedef pair<int, int>pll;
void dijistra()
{
    memset(dist, 0x3f3f3f3f, sizeof dist);
    priority_queue<pll, vector<pll>, greater<pll>>q;
    dist[s] = 0;
    q.push({ 0,s });
    while (q.size())
    {
        auto t = q.top();
        q.pop();
        int d = t.first, num = t.second;
        if (st[num])continue;
        st[num] = true;
        for (int i = h[num]; i != -1; i = ne[i])
        {
            int j = e[i];
            if (dist[j] > dist[num] + w[i])
            {
                dist[j] = dist[num] + w[i];
                q.push({ dist[j],j });
            }
        }
    }
}
void add(int a, int b, int c)
{
    e[idx] = b, ne[idx] = h[a], w[idx] = c,h[a]=idx++;
}
int main()
{
    cin >> n >> m >> s;
    memset(h, -1, sizeof h);
    while (m--)
    {
        int x, y, z;
        cin >> x >> y >> z;
        add(x, y, z);
    }
    dijistra();
    for (int i = 1; i <= n; i++)
    {
        cout << dist[i] << " ";
    }
    return 0;
}

C

因为是无向图，add(x, y, z);
              add(y ,x, z);

#include<iostream>
#include<queue>
#include<cstring>
using namespace std;
const int maxx = 150010;
typedef pair<int, int>PII;
int h[maxx], w[maxx], ne[maxx], e[maxx], dist[maxx], idx;
bool st[maxx];
int n, m,s,t;
void add(int a, int b, int c)
{
    e[idx] = b;
    ne[idx] = h[a];
    w[idx] = c;
    h[a] = idx++;
}
int di()
{
    memset(dist, 0x3f, sizeof dist);
    dist[s] = 0;
    priority_queue<PII, vector<PII>, greater<PII>>q;
    q.push({ 0,s });
    while (q.size())
    {
        PII k = q.top();
        q.pop();
        int ver = k.second, d = k.first;
        if (st[ver])continue;
        st[ver] = true;
        for (int i = h[ver]; i != -1; i = ne[i])
        {
            int j = e[i];
            if (dist[j] > d + w[i])
            {
                dist[j] = d + w[i];
                q.push({ dist[j],j });
            }
        }
    }
  return dist[t];
}
int main()
{
    memset(h, -1, sizeof h);
    cin >> n >> m>> s >> t;
    while (m--)
    {
        int x, y, z;
        cin >> x >> y >> z;
        add(x, y, z);
        add(y ,x, z);
    }
    cout << di() << endl;
    return 0;
}