【每日一题4】AcWing 1113. 红与黑

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Day4 AcWing 1113. 红与黑

拓展

  1. flood fill
    • bfs
    • dfs

代码

宽搜
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#include <iostream>
#include <queue>
#include <algorithm>

#define x first
#define y second

using namespace std;

typedef pair<int, int> PII;
const int N = 25;

int n, m;
char g[N][N];

int bfs(int sx, int sy)
{
    queue<PII> q;
    q.push({sx, sy});
    g[sx][sy] = '#';
    int res = 0;

    int dx[] = {-1, 0, 1, 0}, dy[] = {0, 1, 0, -1};

    while (q.size())
    {
        auto t = q.front();
        q.pop();
        res ++ ;

        for (int i = 0; i < 4; i ++ )
        {
            int x = t.x + dx[i], y = t.y + dy[i];
            if (x < 0 || x >= n || y < 0 || y >= m || g[x][y] != '.') continue;
            g[x][y] = '#';
            q.push({x, y});
        }
    }
    return res;
}

int main()
{
    while (cin >> m >> n, n || m)
    {
        for (int i = 0; i < n; i ++ ) cin >> g[i];
        int x, y;
        for (int i = 0; i < n; i ++ )
            for (int j = 0; j < m; j ++ )
                if (g[i][j] == '@')
                {
                    x = i;
                    y = j;
                }
        cout << bfs(x, y) << endl;
    }

    return 0;
}
深搜
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#include <iostream>

using namespace std;

const int N = 25;

int n, m;
char g[N][N];
int dx[] = {-1, 0, 1, 0}, dy[] = {0, 1, 0, -1};

int dfs(int x, int y)
{
    int res = 1;
    g[x][y] = '#';
    for (int i = 0; i < 4; i ++ )
    {
        int a = x + dx[i], b = y + dy[i];
        if (a >= 0 && a < n && b >= 0 && b < m && g[a][b] == '.')
            res += dfs(a, b);
    }
    return res;
}

int main()
{
    while (cin >> m >> n, n || m)
    {
        for (int i = 0; i < n; i ++ ) cin >> g[i];
        int x, y;
        for (int i = 0; i < n; i ++ )
            for (int j = 0; j < m; j ++ )
                if (g[i][j] == '@')
                {
                    x = i;
                    y = j;
                }
        cout << dfs(x, y) << endl;
    }

    return 0;
}