求助

#include<bits/stdc++.h>
using namespace std;
const int N=1000000+100;
int d[N],vis[N],n,m,s,ans;
vector<int>v[N],v2[N];
vector<int>w[N],w2[N];
queue<int>q;
inline int read()
{
    int z=1,x=0;char c=getchar();
    while(c<'0'||c>'9'){if(c=='-')z=-1;c=getchar();}
    while(c>='0'&&c<='9'){x=(x<<3)+(x<<1)+c-'0';c=getchar();}
    return z*x;
}
void write(int a)
{
    if(a<0){putchar('-');a=-1;}
    if(a>9)write(a/10);
    putchar(a%10+'0');
}
void spfa(int s)
{
    d[s]=0,q.push(s),vis[s]=1;
    while(!q.empty())
    {
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(int i=0;i<v[u].size();i++)
        {
            int x=v[u][i];
            if(d[u]+w[u][i]<d[x])
            {
                d[x]=d[u]+w[u][i];
                if(vis[x]==0)
                {
                    q.push(x);
                    vis[x]=1;
                }
            }
        } 
    }
}
void spfa2(int s)
{
    d[s]=0,q.push(s),vis[s]=1;
    while(!q.empty())
    {
        int u=q.front();
        q.pop();
        vis[u]=0;
        for(int i=0;i<v2[u].size();i++)
        {
            int x=v2[u][i];
            if(d[u]+w2[u][i]<d[x])
            {
                d[x]=d[u]+w2[u][i];
                if(vis[x]==0)
                {
                    q.push(x);
                    vis[x]=1;
                }
            }
        } 
    }
}
int main()
{
    int x,y,z;
    n=read();m=read();
    for(int i=1;i<=n;i++)d[i]=2147483647;
    for(int i=1;i<=m;i++)
    {
        x=read();y=read();z=read();
        v[x].push_back(y);w[x].push_back(z);
        v2[y].push_back(x);w2[y].push_back(z);
    } 
    spfa(1);
    for(int i=1;i<=n;i++)ans+=d[i],d[i]=2147483647;
    memset(vis,0,sizeof(vis));
    spfa2(1);
    for(int i=1;i<=n;i++)ans+=d[i];
    write(ans);
    return 0;
}