最短路变短了（最短路径）

解题思路：

#include<bits/stdc++.h>
using namespace std;
#define ll long long
const int maxn=1e6,inf=INT_MAX;
int head[maxn],cnt,n,m,s,t;
bool vis[maxn];
ll dis1[maxn],dis2[maxn];
struct Edge
{
    int next,to,w;
}edge[maxn];
void add(int u,int v,int w)
{
    edge[++cnt].next=head[u];
    edge[cnt].w=w;
    edge[cnt].to=v;
    head[u]=cnt;
}
struct node
{
    int pos;
    ll d;
    bool operator <(const node& x) const
    {
        return x.d<d;
    }
};
struct e
{
    int x,y,w;
}f[maxn];
void dijkstra(int s)
{
    for(int i=1;i<=n;++i)
        dis2[i]=0x3f3f3f3f3f3f3f3f;
    priority_queue<node> q;
    dis2[s]=0;
    q.push(node{s,0});
    while(!q.empty())
    {
        node now=q.top();
        q.pop();
        int u=now.pos;
        if(vis[u]) continue;
        vis[u]=true;
        for(int i=head[u];i;i=edge[i].next)
        {
            int v=edge[i].to;
            if(dis2[v]>dis2[u]+edge[i].w)
            {
                dis2[v]=dis2[u]+edge[i].w;
                if(!vis[v]) q.push(node{v,dis2[v]});
            }
        }
    }
}
int main()
{
    cin>>n>>m;
    for(int i=1;i<=m;++i)
    {
        scanf("%d%d%d",&f[i].x,&f[i].y,&f[i].w);
        add(f[i].x,f[i].y,f[i].w);
    }
    cin>>t;
    dijkstra(1);
    memcpy(dis1+1,dis2+1,n* sizeof(ll));
    memset(head,0,sizeof(head));
    memset(vis,0,sizeof(vis));
    cnt=0;
    for(int i=1;i<=m;++i)
        add(f[i].y,f[i].x,f[i].w);
    dijkstra(n);
    while(t--)
    {
        int x;
        scanf("%d",&x);
        int u=f[x].x,v=f[x].y;
        if(dis1[n]>f[x].w+dis1[v]+dis2[u]) puts("YES");
        else puts("NO");
    }
    return 0;
}