POJ1256 && 1979 深搜入门

什么是深搜，我现在的理解是：用递归加上一些条件的限制去遍历

简单题，经典题：POJ1526 UVA5712

#include<cstdio>
#include<cstring>

#define M 105

char pic[M][M];
int m,n,idx[M][M];

void DFS(int r,int c,int id)
{
if(r <0 || r >= m || c < 0 || c >= n) return ;  //边界处理
if(idx[r][c] > 0 || pic[r][c] != '@') return ;

idx[r][c] = id;                                 //id顾名思义，说明它属于哪一个油田

for(int dr = -1;dr <= 1; dr++)                  //上下左右的判断
for(int dc = -1;dc <= 1; dc++)
if(dc != 0 || dr != 0)
DFS(dr + r,dc + c,id);
}

int main()
{
while(scanf("%d%d",&m,&n) == 2 && n && m){
for(int i = 0;i < m; i++)
scanf("%s",pic[i]);
memset(idx,0,sizeof(idx));
int cnt = 0;
for(int i = 0;i < m; i++)
for(int j = 0;j < n; j++)
if(idx[i][j] == 0 && pic[i][j] == '@')  //把每一个点找个遍
DFS(i,j,++cnt);
printf("%d\n",cnt);
}
return 0;
}

POJ1979

//题意：从点@出发问能走多少步，‘#’不能走，‘.可以走’
#include<cstdio>
#include<iostream>
using namespace std;

#define M 100
char map[M][M];
int m,n,sum;
int coor[4][2] = {{-1,0},{1,0},{0,-1},{0,1}};

int judge(int x,int y)          //很好的坐标的用法
{
if(x < 0 || x >= m || y < 0 || y >= n) return 0;
return 1;
}

void DFS(int x,int y)
{
int xx,yy;
sum ++;
map[x][y] = '#';        //每次改变，避免重复
for(int i = 0;i < 4; i++){
xx = x + coor[i][0];
yy = y + coor[i][1];
if(judge(xx,yy) && map[xx][yy] == '.')
DFS(xx,yy);
}
}

int main()
{
int x,y;
//    freopen("input.txt","r",stdin);
while(scanf("%d%d",&n,&m) == 2 && n && m){
sum  = 0;
for(int i = 0;i < m; i++){
for(int j = 0;j < n; j++){
cin>>map[i][j];
if(map[i][j] == '@'){
x = i;
y = j;
}
}
}

DFS(x,y);       //很巧妙
printf("%d\n",sum);
}
return 0;
}

现在写的好看一点。

#include<cstdio>

int n,m;
char str[1000][1000];
int a,b,ans;
int dir[4][2] = {{-1,0},{1,0},{0,1},{0,-1}};

void dfs(int x,int y)
{
ans++;
str[x][y] = '#';
for(int i = 0;i < 4; i++){
int xx = x + dir[i][0];
int yy = y + dir[i][1];
if(xx < 1 || xx > m || yy < 1 || yy > n)
continue ;
if(str[xx][yy] == '.'){
dfs(xx,yy);
}
}
}

int main()
{
//freopen("in.txt","r",stdin);
while(scanf("%d%d",&n,&m) != EOF){
if(n == 0 && m == 0)
break;
getchar();
for(int i = 1;i <= m; i++){
for(int j = 1;j <= n; j++){
scanf("%c",&str[i][j]);
if(str[i][j] == '@'){
a = i;
b = j;
}
}
getchar();
}
str[a][b] = '.';
ans = 0;
dfs(a,b);
printf("%d\n",ans);
}
return 0;
}