70分求助

#include<bits/stdc++.h>
#define int long long
using namespace std;
inline int r(){int s=0,k=1;char c=getchar();while(!isdigit(c)){if(c=='-')k=-1;c=getchar();}while(isdigit(c)){s=s*10+c-'0';c=getchar();}return s*k;}
int head[1000001],ans,cnt,n,m;
struct node
{
    int to,dis,next;
}a[1000001];
void add_edge(int from,int to,int dis)
{
    a[++cnt].to=to;
    a[cnt].dis=dis;
    a[cnt].next=head[from];
    head[from]=cnt;
}
int dfs(int u,int fa)
{
    int maxi=0;
    for(int i=head[u];i;i=a[i].next)
    {
        int v=a[i].to;
        if(v==fa)continue;
        int now=dfs(v,u)+a[i].dis;
        if(now>m)ans++;
        else maxi=max(maxi,now);
    }
    return maxi;
}
signed main()
{   
    int x,y,k;
    int maxi=0;
    n=r();
    for(int i=1;i<=n;i++)
    {
        k=r();
        for(int j=1;j<=k;j++)
        {
            x=r();y=r();
            add_edge(i,x,y);
            maxi=max(maxi,y);
        }
    }
    m=r();
    if(maxi>=m)
    {
        cout<<"No solution.";
        return 0;
    }
    dfs(1,0);
    cout<<ans;
}