DFS的一些题2020/3/11

1.

Sample Input
6 9
....#.
.....#
......
......
......
......
......
#@...#
.#..#.
11 9
.#.........
.#.#######.
.#.#.....#.
.#.#.###.#.
.#.#..@#.#.
.#.#####.#.
.#.......#.
.#########.
...........
11 6
..#..#..#..
..#..#..#..
..#..#..###
..#..#..#@.
..#..#..#..
..#..#..#..
7 7
..#.#..
..#.#..
###.###
...@...
###.###
..#.#..
..#.#..
0 0
Sample Output
45
59
6
13

 求解代码

#include <bits/stdc++.h>
using namespace std;

const int N = 100;
bool vis[100][100];
int ans = 0;
char a[100][100];
void DFS(int x, int y) {
	int dir[10] = {0, 0, 1, 0, -1, 1, 0, -1, 0};
	for(int i = 1; i <= 8; i+=2) {
		int temp1 = x, temp2 = y;
		temp1 += dir[i];
		temp2 += dir[i + 1];
		if(temp1 >= 0 && temp2 >= 0 && a[temp1][temp2] == '.' && !vis[temp1][temp2]) {
			ans++;
			a[temp1][temp2] = '!';
			vis[temp1][temp2] = 1;
			DFS(temp1, temp2);
		}
	}
}

int main () {
	int m, n;
	while(cin >> m >> n) {
		memset(a, 0, sizeof a);
		memset(vis, 0, sizeof vis);
		ans = 0;
		if(m == 0 && n == 0) {
			break;
		}
		for(int i = 0; i < n; ++i) {
			cin >> a[i];
		}
		int x, y;
		for(int i = 0; i < n; ++i) {
			for(int j = 0; j < m; ++j) {
				if(a[i][j] == '@') {
					x = i;
					y = j;
				}
			}
		}
		//cout << x << y << endl;
		DFS(x, y);
		cout << ans + 1 << endl;
	}
}

2.

Sample Input
3 4 5
3 2
2 2
3 1
2 3
1 1
Sample Output
4

//POJ 3620
#include <iostream>
using namespace std;
bool vis[110][110];
char a[110][110];
int ans;
int n, m, k;
int temp;
int DFS(int x, int y) {
	temp++;
	int dir[10] = {0, 1, 0, -1, 0, 0, 1, 0, -1};
	for(int i = 1; i <= 8; i += 2) {
		vis[x][y] = 1;	//标记之前的点
		int temp1 = x + dir[i];
		int temp2 = y + dir[i + 1];
		if(temp1 >= 1 && temp2 >= 1 && temp1 <= m && temp2 <= n && !vis[temp1][temp2] && a[temp1][temp2] == '#') {
			DFS(temp1, temp2);
		}
	}
	return temp; 
}
int main () {
	//memset(a, '0', sizeof a);
	cin >> m >> n >> k;
	ans = 0;
	while(k--) {
		int x, y;
		cin >> x >> y;
		a[x][y] = '#';
	}
	// for(int i = 1; i <= n; ++i) {
	// 	for(int j = 1; j <= m; ++j) {
	// 		cout << a[i][j];
	// 	}
	// 	cout << endl;
	// }
	for(int i = 1; i <= m; ++i) {
		for(int j = 1; j <= n; ++j) {
			if(!vis[i][j] && a[i][j] == '#') {
				temp = 0;
				DFS(i, j);
				if(temp > ans) {
					ans = temp;
				}
			}
		}
	}
	cout << ans << endl;
}

 3.

//洛谷1605
#include <bits/stdc++.h>
using namespace std;
bool vis[10][10];
char a[10][10];
int ans;
int sx, sy, ex, ey;
int n, m, t;
void DFS(int x, int y) {
	int dir[10] = {0, 1, 0, -1, 0, 0, 1, 0, -1};
	if(x == ex && y == ey) {
		ans++;
		return;
	}
	for(int i = 1; i <= 8; i += 2) {
		vis[x][y] = 1;	//标记之前的点
		int temp1 = x + dir[i];
		int temp2 = y + dir[i + 1];
		if(temp1 >= 1 && temp2 >= 1 && temp1 <= n && temp2 <= m && !vis[temp1][temp2] && a[temp1][temp2] != '#') {
			DFS(temp1, temp2);
			vis[temp1][temp2] = 0;
			//进行回溯
		}
	}
}
int main () {

	cin >> n >> m >> t;
	cin >> sx >> sy >> ex >> ey;
	ans = 0;
	while(t--) {
		int x, y;
		cin >> x >> y;
		a[x][y] = '#';
	}
	DFS(sx, sy);
	cout << ans << endl;
}