poj3271 Lilypad Pond bfs

处理出每个点一步能到的点再统计路径。

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
#include <algorithm>
using namespace std;
int dx[9]={0,-2,-2,-1,-1,1,1,2,2};
int dy[9]={0,-1,1,-2,2,-2,2,-1,1};
const int maxn=30+9;
int dist[maxn][maxn],a[maxn][maxn];
int n,m;
bool d[maxn][maxn][maxn][maxn];
long long ans[maxn][maxn];
bool text[maxn][maxn];
bool ok(int x,int y)
{if(x>0&&x<=n&&y>0&&y<=m)return  true;return false;
}
void bfs2(int x,int y)
{queue<int>qx,qy;qx.push(x);qy.push(y);memset(dist,0x3f3f3f3f,sizeof(dist));memset(ans,0,sizeof(ans));dist[x][y]=0;ans[x][y]=1;while(!qx.empty()){int tx=qx.front();int ty=qy.front();qx.pop();qy.pop();if(a[tx][ty]==2) continue;for(int i=1;i<=n;i++){for(int j=1;j<=m;j++){if(d[tx][ty][i][j]){if(dist[i][j]==dist[tx][ty]+1)ans[i][j]+=ans[tx][ty];else if(dist[i][j]>dist[tx][ty]+1){dist[i][j]=dist[tx][ty]+1;ans[i][j]=ans[tx][ty];qx.push(i);qy.push(j);}}}}}
}
void bfs(int x,int y)
{memset(text,0,sizeof(text));queue<int>qx,qy;qx.push(x);qy.push(y);text[x][y]=1;while(!qx.empty()){int tx=qx.front();int ty=qy.front();qx.pop();qy.pop();for(int i=1;i<=8;i++){int xx=tx+dx[i];int yy=ty+dy[i];if(!ok(xx,yy)) continue;if(text[xx][yy]) continue;text[xx][yy]=1;if(a[xx][yy]==1){qx.push(xx);qy.push(yy);}else{d[x][y][xx][yy]=1;}}}
}
int main()
{scanf("%d %d",&n,&m);{int t,s,tox,toy;for(int i=1;i<=n;i++)for(int j=1;j<=m;j++){scanf("%d",&a[i][j]);if(a[i][j]==3){t=i;s=j;}else if(a[i][j]==4){tox=i;toy=j;}}memset(d,0,sizeof(d));for(int i=1;i<=n;i++)for(int j=1;j<=m;j++)bfs(i,j);bfs2(t,s);if(dist[tox][toy]>1e3){printf("-1\n");}else{printf("%d\n%lld\n",dist[tox][toy]-1,ans[tox][toy]);}}return 0;
}

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