不撞南牆不回頭———深度優先搜尋（DFS）Oil Deposits

標籤：

Oil Deposits

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 23018    Accepted Submission(s): 13272

Problem DescriptionThe GeoSurvComp geologic survey company is responsible for detecting underground oil deposits. GeoSurvComp works with one large rectangular region of land at a time, and creates a grid that divides the land into numerous square plots. It then analyzes each plot separately, using sensing equipment to determine whether or not the plot contains oil. A plot containing oil is called a pocket. If two pockets are adjacent, then they are part of the same oil deposit. Oil deposits can be quite large and may contain numerous pockets. Your job is to determine how many different oil deposits are contained in a grid.  

 

InputThe input file contains one or more grids. Each grid begins with a line containing m and n, the number of rows and columns in the grid, separated by a single space. If m = 0 it signals the end of the input; otherwise 1 <= m <= 100 and 1 <= n <= 100. Following this are m lines of n characters each (not counting the end-of-line characters). Each character corresponds to one plot, and is either `*‘, representing the absence of oil, or `@‘, representing an oil pocket. 

 

OutputFor each grid, output the number of distinct oil deposits. Two different pockets are part of the same oil deposit if they are adjacent horizontally, vertically, or diagonally. An oil deposit will not contain more than 100 pockets. 

 

Sample Input1 1*3 5*@*@***@***@*@*1 8@@****@*5 5 ****@*@@*@*@**@@@@*@@@**@0 0  

 

Sample Output0122    剛剛學了深搜，做一下總結。DFS按著一條路走到，不撞南牆不回頭，回的話也是回到上一次最近調用dfs()函數的地方，然後看看是否還有滿足條件的，如果有則按滿足條件的那個地方一直往下搜尋（追根究底，一直往下，一直），直到撞南牆，深搜就是把所有的地方都遍曆一次，一個也不放過 新手總結，不到指出請大家指正！！ 附代碼：

#include <stdio.h>
#include <string.h>
int m,n,total = 0,book[101][101];
char c[101][101];
int next[8][2]=
{
{0,1},//右
{1,1},//右下
{1,0},//下
{1,-1},//左下
{0,-1},//左
{-1,-1},//左上
{-1,0},//上
{-1,1}//右上
};

void dfs(int x,int y)
{
int tx,ty,k;
for(k=0;k<8;k++)
{
tx = x+next[k][0];
ty = y+next[k][1];

if(tx<1||ty<1||tx>m||ty>n)
{
continue;
}
if(c[tx][ty]==‘@‘&&book[tx][ty]==0)
{
//total++;//這裡不能加1 ，因為是跟上一個連著的油田，都算是一塊油田
book[tx][ty] = 1;
dfs(tx,ty);//8個中有一個滿足條件，以這一個為中心，繼續往下搜，如果不滿足條件，返回來，接著上一次沒搜完的搜
//book[tx][ty] = 0;//每一格就走一次，搜過了不再搜
}
}
return;
}
int main()
{
int i,j;
while(scanf("%d%d",&m,&n)&&m!=0)
{
getchar();
total = 0;
memset(book,0,sizeof(book));
for(i=1;i<=m;i++){
for(j=1;j<=n;j++){
scanf("%c",&c[i][j]);
}
getchar();
}
for(i=1;i<=m;i++)
{
for(j=1;j<=n;j++)
{
if(c[i][j]==‘@‘ && book[i][j]==0)
{
total++;//加它本身
dfs(i,j);//對它的八個方向進行搜尋
}
}
}
printf("%d\n",total);
}
return 0;
}

不撞南牆不回頭———深度優先搜尋（DFS）Oil Deposits