2019.4.27 提高B组 T4 nssl-1319 埃雷萨拉斯寻宝

版权声明：虽然本蒟蒻很菜，但各位dalao转载请注明出处谢谢。 https://blog.csdn.net/xuxiayang/article/details/89602087

$Descrption$

给定到达别的数字的代价，求从第一行的数字到最后一行的数字的最大剩余代价

数据范围： $n\leq 50$

---

$Solution$

$spfa$呀QWQ

---

$Floyd\ TLE\ Code$

#include<cstdio>
#include<cctype>
#include<cstring>
#include<algorithm>
using namespace std;int n,map[501][501],dis[25001],Ans=-0x3f3f3f3f,p,xl,f[2051][2051];
const int dx[4]={-1,0,1,0};
const int dy[4]={0,1,0,-1};
inline int read()
{
    char c;int f=0,d=1;
    while(c=getchar(),!isdigit(c)) if(c=='-') d=-1;f=(f<<3)+(f<<1)+c-48;
    while(c=getchar(),isdigit(c)) f=(f<<3)+(f<<1)+c-48;
    return d*f;
}
signed main()
{
	memset(f,0x3f,sizeof(f));
	n=read();p=read();xl=read();
	for(register int i=1;i<=p;i++) dis[i]=read(),f[i][i]=0;
	for(register int i=1;i<=n;i++) for(register int j=1;j<=n;j++) map[i][j]=read();
	for(register int i=1;i<=n;i++)
	 for(register int j=1;j<=n;j++)
	{
		int ys=map[i][j];
		for(register int k=0;k<4;k++)
		{
			int nx=i+dx[k],ny=j+dy[k],nys=map[nx][ny];
			if(nx<1||nx>n||ny<1||ny>n||ys==nys) continue;
			f[ys][nys]=min(f[ys][nys],dis[nys]);
		}
	}
	for(register int k=1;k<=p;k++)
	 for(register int i=1;i<=p;i++)
	  for(register int j=1;j<=p;j++)
	   f[i][j]=min(f[i][j],f[i][k]+f[k][j]);
	for(register int i=1;i<=n;i++)
	 for(register int j=1;j<=n;j++)
	  Ans=max(Ans,xl-f[map[1][i]][map[n][j]]-dis[map[1][i]]);
	if(Ans<1) return puts("NO"); 
	printf("%d",Ans);
}

---

$SPFA\ AC\ Code$

#include<queue>
#include<cstdio>
#include<cctype>
#include<vector>
#include<cstring>
#define id(x,y) (x-1)*n+y
#define LL long long
#define from_ys map[i][j]
#define to_ys map[i+dx[k]][j+dy[k]]
#define tox i+dx[k]
#define toy j+dy[k]
using namespace std;int n,map[51][51],dis[2501],ans[2501],xl,p,l[2501],tot,Ans=-0x3f3f3f3f;
bool check[2501],vis[2501];
struct node{int next,to,w;}e[12500001];
inline void add(int u,int v,int w){e[++tot]=(node){l[u],v,w};l[u]=tot;return;}
const int dx[4]={-1,0,1,0};
const int dy[4]={0,1,0,-1};
inline LL read()
{
    char c;int f=0,d=1;
    while(c=getchar(),!isdigit(c)) if(c=='-') d=-1;f=(f<<3)+(f<<1)+c-48;
    while(c=getchar(),isdigit(c)) f=(f<<3)+(f<<1)+c-48;
    return d*f;
}
inline void spfa(int S)
{
	memset(ans,0x3f,sizeof(ans));
	memset(vis,0,sizeof(vis));
	check[map[1][S]]=true;
	queue<int>q;
	q.push(S);ans[S]=dis[map[1][S]];vis[S]=true;
	while(q.size())
	{
		int x=q.front();q.pop();
		for(register int i=l[x];i;i=e[i].next)
		{
			int y=e[i].to,w=e[i].w;
			if(ans[y]>ans[x]+w)
			{
				ans[y]=ans[x]+w;
				if(!vis[y]) vis[y]=true,q.push(y);
			}
		}
		vis[x]=false;
	}
	for(register int i=1;i<=n;i++) Ans=max(Ans,xl-ans[id(n,i)]);
	return;
}
signed main()
{
	n=read();p=read();xl=read();
	for(register int i=1;i<=p;i++) dis[i]=read();
	for(register int i=1;i<=n;i++) for(register int j=1;j<=n;j++) map[i][j]=read();
	for(register int i=1;i<=n;i++)
	 for(register int j=1;j<=n;j++)
	{
		for(register int k=0;k<4;k++) if(from_ys!=to_ys&&tox>0&&tox<=n&&toy>0&&toy<=n) add(id(i,j),id(tox,toy),dis[to_ys]);
		for(register int k=1;k<=n;k++)
		 for(register int l=1;l<=n;l++)
		  if(map[i][j]==map[k][l]&&(i!=k||j!=l))
		   add(id(i,j),id(k,l),0);
	}
	for(register int i=1;i<=n;i++) if(!check[map[1][i]]) spfa(i);
	if(Ans<1) return puts("NO")&0;
	printf("%d",Ans);
}