poj 2386（深搜或广搜）

偏执的太偏执、 2022-08-25 13:46 197阅读 0赞

Lake Counting

<table> 
 <tbody> 
  <tr> 
   <td><strong>Time Limit:</strong>&nbsp;1000MS</td> 
   <td>&nbsp;</td> 
   <td><strong>Memory Limit:</strong>&nbsp;65536K</td> 
  </tr> 
  <tr> 
   <td><strong>Total Submissions:</strong>&nbsp;17917</td> 
   <td>&nbsp;</td> 
   <td><strong>Accepted:</strong>&nbsp;9069</td> 
  </tr> 
 </tbody> 
</table>

Description

Due to recent rains, water has pooled in various places in Farmer John's field, which is represented by a rectangle of N x M (1 <= N <= 100; 1 <= M <= 100) squares. Each square contains either water ('W') or dry land ('.'). Farmer John would like to figure out how many ponds have formed in his field. A pond is a connected set of squares with water in them, where a square is considered adjacent to all eight of its neighbors.  
  
Given a diagram of Farmer John's field, determine how many ponds he has.

Input

\* Line 1: Two space-separated integers: N and M  
  
\* Lines 2..N+1: M characters per line representing one row of Farmer John's field. Each character is either 'W' or '.'. The characters do not have spaces between them.

Output

\* Line 1: The number of ponds in Farmer John's field.

Sample Input

10 12
    W........WW.
    .WWW.....WWW
    ....WW...WW.
    .........WW.
    .........W..
    ..W......W..
    .W.W.....WW.
    W.W.W.....W.
    .W.W......W.
    ..W.......W.

Sample Output

这道题目比较基础，可以深搜也可以广搜

深搜快一点 36ms，广搜47ms。很好的练习题目。

把注释的去掉就是深搜了。

#include <stdio.h>
    #include <queue>
    using namespace std;
    #define N 102
    
    char map[N][N];
    int n,m;
    struct Node
    {
        int x,y;
    };
    int dis[10][3]={ {0,1},{0,-1},{-1,0},{1,0},{-1,-1},{-1,1},{1,-1},{1,1} };
    void search(int a,int b)
    {
        /*map[a][b]='.';
        for(int i=0;i<8;i++)
        {
            int tmpx=a+dis[i][0];
            int tmpy=b+dis[i][1];
            if(tmpx>0 && tmpx<=n && tmpy>0 && tmpy<=m && map[tmpx][tmpy]=='W' ){
                //map[tmpx][tmpy]='.';
                search(tmpx,tmpy);
            }
        }*/
        Node tmp,be;
        be.x=a,be.y=b;
        queue<Node> v;
        v.push(be);
        map[a][b]='.';
        while(!v.empty())
        {
            be=v.front();
            v.pop();
            for(int i=0;i<8;i++)
            {
                tmp.x=be.x+dis[i][0];
                tmp.y=be.y+dis[i][1];
                if(tmp.x>0 && tmp.x<=n && tmp.y>0 && tmp.y<=m && map[tmp.x][tmp.y]=='W' )
                {
                    v.push(tmp);
                    map[tmp.x][tmp.y]='.';
                }
            }
        }
    }
    
    int main()
    {
        int i,j,count;
        while(~scanf("%d %d",&n,&m))
        {
            getchar();
            count=0;
            for(i=1;i<=n;i++){
                for(j=1;j<=m;j++){
                    scanf("%c",&map[i][j]);}  ///缺了括号，害死人啊
                getchar();}
            for(i=1;i<=n;i++)
                for(j=1;j<=m;j++)
                    if(map[i][j]=='W')
                    {
                        //printf("%d %d\n",i,j);
                        search(i,j);count++;
                    }
            printf("%d\n",count);
        }
        return 0;
    }

深搜递归写法

#include <stdio.h>
    #include <queue>
    using namespace std;
    #define N 102
    
    char map[N][N];
    int n,m;
    
    void search(int i,int j)
    {
        if(map[i][j-1]=='W') { map[i][j-1]='.'; search(i,j-1); }
        if(map[i][j+1]=='W') { map[i][j+1]='.'; search(i,j+1); }
        if(map[i-1][j]=='W') { map[i-1][j]='.'; search(i-1,j); }
        if(map[i+1][j]=='W') { map[i+1][j]='.'; search(i+1,j); }
        if(map[i-1][j-1]=='W') { map[i-1][j-1]='.'; search(i-1,j-1); }
        if(map[i-1][j+1]=='W') { map[i-1][j+1]='.'; search(i-1,j+1); }
        if(map[i+1][j-1]=='W') { map[i+1][j-1]='.'; search(i+1,j-1); }
        if(map[i+1][j+1]=='W') { map[i+1][j+1]='.'; search(i+1,j+1); }
    }
    
    int main()
    {
        int i,j,count;
        while(~scanf("%d %d",&n,&m))
        {
            getchar();
            count=0;
            for(i=1;i<=n;i++){
                for(j=1;j<=m;j++){
                    scanf("%c",&map[i][j]);}  ///缺了括号，害死人啊
                getchar();}
            for(i=1;i<=n;i++)
                for(j=1;j<=m;j++)
                    if(map[i][j]=='W')
                    {
                        //printf("%d %d\n",i,j);
                        search(i,j);count++;
                    }
            printf("%d\n",count);
        }
        return 0;
    }