Acwing-1113. 红与黑

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DFS解法：

复制代码

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#include <iostream>
#include <algorithm>
#include <cstring>

using namespace std;

const int N = 25;

char g[N][N];
bool st[N][N];
int w, h, res;
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};

void dfs(int x, int y)
{
    if (g[x][y] == '#') return ;
    
    st[x][y] = true;
    res ++;
    for (int i = 0; i < 4; ++ i)
    {
        int a = x + dx[i], b = y + dy[i];
        if (a < 0 || a >= h || b < 0 || b >= w || st[a][b]) continue;
        
        dfs(a, b);
    }
}

int main()
{
    while (cin >> w >> h && w && h)
    {
        memset(st, 0, sizeof(st));
        for (int i = 0; i < h; ++ i) cin >> g[i];
        
        res = 0;
        for (int i = 0; i < h; ++ i)
            for (int j = 0; j < w; ++ j)
                if (g[i][j] == '@') dfs(i, j);
        
        printf("%dn", res);
    }
    return 0;
}

BFS解法：

复制代码

#include <iostream>
#include <algorithm>
#include <cstring>
#include <queue>

using namespace std;

typedef pair<int, int> PII;

const int N = 25;

char g[N][N];
queue<PII> q;
int w, h;
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};

int dfs(int x, int y)
{
    int res = 0;
    q.push({x, y});
    g[x][y] = '#';
    
    while (q.size())
    {
        auto t = q.front();
        q.pop();
        res ++;
        
        int x = t.first, y = t.second;
        for (int i = 0; i < 4; ++ i)
        {
            int a = x + dx[i], b = y + dy[i];
            if (a < 0 || a >= h || b < 0 || b >= w || g[a][b] == '#') continue;
            g[a][b] = '#';
            q.push({a, b});
        }
    }
    
    return res;
}

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

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#include <iostream>
#include <algorithm>
#include <cstring>
#include <queue>

using namespace std;

typedef pair<int, int> PII;

const int N = 25;

char g[N][N];
queue<PII> q;
int w, h;
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};

int dfs(int x, int y)
{
    int res = 0;
    q.push({x, y});
    g[x][y] = '#';
    
    while (q.size())
    {
        auto t = q.front();
        q.pop();
        res ++;
        
        int x = t.first, y = t.second;
        for (int i = 0; i < 4; ++ i)
        {
            int a = x + dx[i], b = y + dy[i];
            if (a < 0 || a >= h || b < 0 || b >= w || g[a][b] == '#') continue;
            g[a][b] = '#';
            q.push({a, b});
        }
    }
    
    return res;
}

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