bzoj1619 / P2919 [USACO08NOV]守护农场Guarding the Farm

Posted 2021-01-15 kafuuchino

P2919 [USACO08NOV]守护农场Guarding the Farm

相似题：P3456 [POI2007]GRZ-Ridges and Valleys

每次bfs海拔相同的块，根据与周围的块的大小关系判断是否是山丘。

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<queue>
 5 #include<cctype>
 6 #define re register
 7 using namespace std;
 8 void read(int &x){
 9     char c=getchar();x=0;
10     while(!isdigit(c)) c=getchar();
11     while(isdigit(c)) x=(x<<3)+(x<<1)+(c^48),c=getchar();
12 }
13 #define N 702
14 const int d1[8]={0,1,0,-1,1,1,-1,-1};
15 const int d2[8]={1,0,-1,0,1,-1,1,-1};
16 struct data{int x,y;};
17 int n,m,H[N][N],ans; bool vis[N][N];
18 void bfs(int f1,int f2){
19     queue <data> h; h.push((data){f1,f2});
20     vis[f1][f2]=1; int p=1;
21     while(!h.empty()){
22         data u=h.front(); h.pop();
23         for(int i=0;i<8;++i){
24             int r1=u.x+d1[i],r2=u.y+d2[i];
25             if(r1<1||r1>n||r2<1||r2>m) continue;
26             p&=(H[r1][r2]<=H[u.x][u.y]);//是否是山丘
27             if(vis[r1][r2]) continue;
28             if(H[r1][r2]==H[u.x][u.y])
29                 h.push((data){r1,r2}),vis[r1][r2]=1;
30         }
31     }ans+=p;
32 }
33 int main(){
34     read(n);read(m);
35     for(re int i=1;i<=n;++i)
36         for(re int j=1;j<=m;++j)
37             read(H[i][j]);
38     for(re int i=1;i<=n;++i)
39         for(re int j=1;j<=m;++j)
40             if(!vis[i][j]) bfs(i,j);
41     printf("%d",ans);
42     return 0;
43 }

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