POJ_2386: Lake Counting
2013-08-03 23:14
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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
Sample Output
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
备注:简单的dfs数连通分量个数。
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
备注:简单的dfs数连通分量个数。
#include<stdio.h> #define LAND -1 #define WATER 1 int N,M; int graph[101][101]; int visited[101][101]; void dfs(int startA,int startB) { visited[startA][startB]=true; if(startA-1>=0 && !visited[startA-1][startB] && graph[startA-1][startB]==WATER) dfs(startA-1,startB); if(startA+1<N && !visited[startA+1][startB] && graph[startA+1][startB]==WATER) dfs(startA+1,startB); if(startB-1>=0 && !visited[startA][startB-1] && graph[startA][startB-1]==WATER) dfs(startA,startB-1); if(startB+1<M && !visited[startA][startB+1] && graph[startA][startB+1]==WATER) dfs(startA,startB+1); if(startA-1>=0 && startB-1>=0 && !visited[startA-1][startB-1] && graph[startA-1][startB-1]==WATER) dfs(startA-1,startB-1); if(startA-1>=0 && startB+1<M && !visited[startA-1][startB+1] && graph[startA-1][startB+1]==WATER) dfs(startA-1,startB+1); if(startA+1<N && startB-1>=0 && !visited[startA+1][startB-1] && graph[startA+1][startB-1]==WATER) dfs(startA+1,startB-1); if(startA+1<N && startB+1<M && !visited[startA+1][startB+1] && graph[startA+1][startB+1]==WATER) dfs(startA+1,startB+1); } int main() { scanf("%d %d",&N,&M); getchar(); for(int i=0;i<N;i++) { for(int j=0;j<M;j++) { char c; c=getchar(); if(c=='.') graph[i][j]=LAND; else if(c=='W') graph[i][j]=WATER; visited[i][j]=false; } getchar(); } //count connected components using dfs int count=0; for(int i=0;i<N;i++) for(int j=0;j<M;j++) { if(!visited[i][j] && graph[i][j]==WATER) { dfs(i,j); count++; } } printf("%d\n",count); return 0; }
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