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POJ 2386 Lake Counting
来源:http://poj.org/problem?id=2386
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Lake Counting
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 3 Hint
OUTPUT DETAILS:
There are three ponds: one in the upper left, one in the lower left,and one along the right side. Source
USACO 2004 November
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题意:题意题意！。！
一句话两处理解错误,,,,, 求一块田野里有多少块水域～～ 里面最关键的一句：A pond is a connected set of squares with water in them, where a square
is considered adjacent to all eight of its neighbors.
開始理解成至少要两个"W"才算一块水域---还有方向，仅仅考虑上下左右四个方向，导致一直WA..
题解: DFS(感觉又不是标准的DFS。不须要回溯)....
AC代码:
#include<iostream>
#include<string>
using namespace std;
int dir[8][2]={
{0,1},{0,-1},
{1,0},{-1,0},
{1,1},{1,-1},
{-1,-1},{-1,1}
};
string map[105];
int dx,dy,count=0;
bool flag;
void dfs(int x,int y){
for(int i=0;i<8;i++){
int tempx=x+dir[i][0],tempy=y+dir[i][1];
if(tempx>=0&&tempx<dx&&tempy>=0&&tempy<dy&&map[tempx][tempy]==‘W‘){
map[tempx][tempy]=‘.‘;
dfs(tempx,tempy);
}
}
}
int main()
{
cin>>dx>>dy;
for(int i=0;i<dx;i++)
cin>>map[i];
for(int i=0;i<dx;i++)
for(int j=0;j<dy;j++){
if(map[i][j]==‘W‘){
count++;
map[i][j]=‘.‘;
dfs(i,j);
}
}
cout<<count<<endl;
return 0;
}
POJ 2386 Lake Counting
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