POJ 1111 Image Perimeters

1. 写得最有逻辑的一道题了，10次讲座学的最好的就是DFS和BFS了。

2. 直接深搜

#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>
#include <cstring>
#include <stack>
#include <queue>
#include <climits>
#include <cstdio>
#include <cmath>

using namespace std;
int a, b, sx, sy;
char map[25][25];
int num[25][25];
bool flag[25][25];
int dir[8][2] = {{-1, -1}, {0, -1}, {1, -1}, {1, 0}, {1, 1}, {0, 1}, {-1, 1}, {-1, 0}};
bool check(int x, int y)
{
    return (x > 0 && x <= a && y > 0 && y <= b) ? true : false;
}
void dfs(int x, int y)
{
    int nextx, nexty;
    flag[x][y] = 1;
    for (int i = 0; i < 8; i++)
    {
        nextx = x + dir[i][0];
        nexty = y + dir[i][1];
        if ((dir[i][0] == 0 || dir[i][1] == 0) && map[nextx][nexty] != 'X')
            num[x][y]++;
        if (check(nextx, nexty) && map[nextx][nexty] == 'X' && flag[nextx][nexty] == 0)
            dfs(nextx, nexty);
    }
}
void init()
{
    for (int i = 0; i < 25; i++)
        for (int j = 0; j < 25; j++)
            map[i][j] = '.';
    memset(num, 0, sizeof(num));
    memset(flag, 0, sizeof(flag));
}
int main()
{
    int i, j, ans;
    while (cin >> a >> b >> sx >> sy)
    {
        if (!a && !b)
            break;
        init();
        for (i = 1; i <= a; i++)
            for (j = 1; j <= b; j++)
                cin >> map[i][j];
        dfs(sx, sy);
        ans = 0;
        for (i = 1; i <= a; i++)
            for (j = 1; j <= b; j++)
                ans += num[i][j];
        cout << ans << endl;
    }
    return 0;
}