#include<bits/stdc++.h>
using namespace std;

int main()
{
    double a=1.15;
    printf("%.15lf\n",a);
    printf("%.16lf\n",a);
    printf("%.1lf\n",a);
}

输出：
1.150000000000000
1.1499999999999999
1.1

AC代码

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
const int N=1050;

int n1,n2,m,range;
vector<PII> g[N];
int dist[N];
bool st[N];
int ans1;
int ans2=-1000;
double ans3=1e18;
void dij(int s)
{
    memset(dist,0x3f,sizeof dist);
    dist[s]=0;
    queue<int> q;
    q.push(s);
    st[s]=true;
    while(q.size())
    {
        int x=q.front();q.pop();
        st[x]=false;
        for(auto edge: g[x])
        {
            int v=edge.first,d=edge.second;
            if(dist[v]>dist[x]+d)
            {
                dist[v]=dist[x]+d;
                if(!st[v]) st[v]=true,q.push(v);
            }
        }
    }
    long long sum=0;
    int minv=INT_MAX;
    for(int i=1;i<=n1;i++) 
    {
       // cout<<dist[i]<<endl;    
        if(dist[i]>range) return;
        sum+=dist[i];
        minv=min(minv,dist[i]);
    }
    double ave=(double)sum/n1;
    if(ans2<minv)
    {
        ans2=minv;
        ans1=s;
        ans3=ave;
    }else if(ans2==minv&&ans3>ave) ans1=s,ans3=ave;
}

int main()
{
    cin>>n1>>n2>>m>>range;

    while(m--)
    {
        string x,y;
        int z,a,b;
        cin>>x>>y>>z;
        if(x[0]=='G') a=1000+stoi(x.substr(1));
        else a=stoi(x);
        if(y[0]=='G') b=1000+stoi(y.substr(1));
        else b=stoi(y);
        g[a].push_back({b,z});
        g[b].push_back({a,z});
    }

    for(int i=1;i<=n2;i++)
    {
        dij(1000+i);
    }
    if(!ans1) puts("No Solution");
    else printf("G%d\n%.1lf %.1lf",ans1-1000,(double)ans2,ans3+1e-8);
    return 0;
}