poj3278 <BFS/DFS>

the reason of falure:1、记得不能给数组A[负数]赋值,会running error

2、定义数组应该在头文件那#define MAXN 9999

然后定义的全局变量

thinking：1、<BFS>从8个方向都探索,如果有W则给打上标记,放入队列.

2、<DFS>从8个方向都搜索,当有W则打上标记,马上从这个打上标记的W开始搜索下一个

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

Sample Output

3

Hint

OUTPUT DETAILS: 

There are three ponds: one in the upper left, one in the lower left,and one along the right side

BFS代码:

#include <iostream>#include <queue>#define MAXN 200using namespace std;struct ttt{int x,y;};int dr[]={-1,0,1,0,1,-1,-1,1};int dc[]={0,1,0,-1,1,-1,1,-1};int n,m;char map1[MAXN][MAXN];bool walked[MAXN][MAXN];void fun(ttt b){queue<ttt>q;ttt a;q.push(b);while(!q.empty()){b=q.front();q.pop();for(int i=0;i<8;i++){a.x=b.x+dr[i];a.y=b.y+dc[i];if(a.x<=m&&a.x>=1&&a.y<=n&&a.y>=1&&walked[a.y][a.x]==0&&map1[a.y][a.x]=='W'){walked[a.y][a.x]=1;q.push(a);}}}}int main(){freopen("in.txt","r",stdin);freopen("out.txt","w",stdout);cin >> n >> m;int i,j,k,l;ttt a;int sum=0;for(i=1;i<=n;i++)for(j=1;j<=m;j++)cin >> map1[i][j];for(i=1;i<=n;i++)for(j=1;j<=m;j++)if(walked[i][j]==0&&map1[i][j]=='W'){walked[i][j]=1;sum++;a.x=j;a.y=i;fun(a);}cout << sum << endl;return 0;}

DFS代码:

#include <iostream>#define MAXN 300using namespace std;char map1[MAXN][MAXN];int n,m;bool walked[MAXN][MAXN];int dr[]={-1,0,1,0,1,-1,-1,1};int dc[]={0,1,0,-1,1,-1,1,-1};void dfs(int i,int j){if(i<1||i>n||j<1||j>m)return;for(int k=0;k<8;k++){int a=i+dr[k];int b=j+dc[k];if(map1[a][b]=='W'&&walked[a][b]==0){walked[a][b]=1;dfs(a,b);}}}int main(){freopen("in.txt","r",stdin);freopen("out.txt","w",stdout);cin >> n >> m;int i,j,k,l;int sum=0;for(i=1;i<=n;i++)for(j=1;j<=m;j++)cin >> map1[i][j];for(i=1;i<=n;i++)for(j=1;j<=m;j++)if(walked[i][j]==0&&map1[i][j]=='W'){walked[i][j]=1;dfs(i,j);sum++;}cout << sum << endl;return 0;}