POJ 2386 Lake Counting
阿新 • • 發佈：2017-06-02
family 回溯 [0 tab rep sep miss hint pac
來源:http://poj.org/problem?id=2386
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 * 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 |
題意:題意題意！。！
一句話兩處理解錯誤,,,,, 求一塊田野裏有多少塊水域～～ 裏面最關鍵的一句：A pond is a connected set of squares with water in them, where a square
is considered adjacent to all eight of its neighbors.
開始理解成至少要兩個"W"才算一塊水域---還有方向，僅僅考慮上下左右四個方向，導致一直WA..
題解: DFS(感覺又不是標準的DFS。不須要回溯)....
AC代碼:
#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