C++逛公园

题目：

代码：

#include <bits/stdc++.h>
using namespace std;
 
const int Maxn=100010;
const int Maxm=200010;
int t,n,m,size,k,mod,ans,minn,flag;
int dis[Maxn],First[Maxn],first[Maxn],f[Maxn][55],vis[Maxn][55];
struct shu{int to,next,len;};
shu Edge[Maxm],edge[Maxm];
priority_queue<pair<int,int> >q;
 
inline int get_int()
{
	int x=0,f=1;
	char c;
	for(c=getchar();(!isdigit(c))&&(c!='-');c=getchar());
	if(c=='-') {f=-1;c=getchar();}
	for(;isdigit(c);c=getchar()) x=(x<<3)+(x<<1)+c-'0';
	return x*f;
}
 
inline void clean()
{
	size=ans=flag=0;
	memset(dis,0x3f3f3f,sizeof(dis));
	memset(First,0,sizeof(First));
	memset(first,0,sizeof(first));
	memset(f,-1,sizeof(f));
	memset(vis,0,sizeof(vis));
}
 
inline void build(int x,int y,int z)
{
	Edge[++size].next=First[x];
	First[x]=size;
	Edge[size].to=y,Edge[size].len=z;
	edge[size].next=first[y];
	first[y]=size;
	edge[size].to=x,edge[size].len=z;
}
 
inline void dijkstra()
{
	q.push(make_pair(0,1)),dis[1]=0;
	while(!q.empty())
	{
	  int point=q.top().second;
	  q.pop();
	  for(int u=First[point];u;u=Edge[u].next)
	  {
	  	int to=Edge[u].to;
	  	if(dis[to] > dis[point] + Edge[u].len)
	  	{
	  	  dis[to]=dis[point] + Edge[u].len;
	  	  q.push(make_pair(-dis[to],to));
	  	}
	  }
	}
}
 
inline int dfs(int point,int k)
{
	if(~f[point][k]) return f[point][k];
	f[point][k]=0,vis[point][k]=1;
	for(register int u=first[point];u;u=edge[u].next)
	{
	  int to=edge[u].to,num=dis[point]-dis[to]+k-edge[u].len;
	  if(num<0) continue;
	  if(vis[to][num]) flag=1;
	  f[point][k]=(f[point][k]+dfs(to,num))%mod;
	}
	vis[point][k]=0;
	return f[point][k];
}
 
int main()
{
	t=get_int();
	while(t--)
	{
	  clean();
	  n=get_int(),m=get_int(),k=get_int(),mod=get_int();
	  for(int i=1;i<=m;i++)
	  {
	  	int x=get_int(),y=get_int(),z=get_int();
	  	build(x,y,z);
	  }
	  dijkstra();
	  if(!dis[n]) {cout<<"-1\n";continue;}
	  f[1][0]=1;
	  for(int i=0;i<=k;i++) ans=(ans+dfs(n,i))%mod;
	  if(!flag) cout<<ans<<"\n";
	  else cout<<"-1\n";
	}
	return 0;
}