DFS之连通性模型 AcWing 1113. 红与黑

向右看齐 2024-04-07 10:19 35阅读 0赞

## DFS之连通性模型 AcWing 1113. 红与黑 ##

### 原题链接 ###

[AcWing 1113. 红与黑][AcWing 1113.]

### 算法标签 ###

DFS Flood Fill

### 思路 ###

1.找到字符’@’  
2.dfs向四周搜索，直至遇到’\#’，搜素后用一个数组标记  
![在这里插入图片描述][c7f4b951cf2f43b18d87ef29affe42b1.png]

#include<bits/stdc++.h>
    #define int long long
    #define rep(i, a, b) for(int i=a;i<b;++i)
    #define Rep(i, a, b) for(int i=a;i>b;--i)
    #define x first
    #define y second
    #define ump unordered_map
    #define pq priority_queue
    using namespace std;
    typedef pair<int, int> PII;
    const int N=25;
    int n, m;
    char g[N][N];
    bool st[N][N];
    int dx[4]={0, 1, 0, -1}, dy[4]={1, 0, -1, 0};
    inline int rd(){
       int s=0,w=1;
       char ch=getchar();
       while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
       while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
       return s*w;
    }
    void put(int x) {
        if(x<0) putchar('-'),x=-x;
        if(x>=10) put(x/10);
        putchar(x%10^48);
    }
    int dfs(int xa, int ya){
        int cnt=1;
        st[xa][ya]=true;
        rep(i, 0, 4){
            int x=xa+dx[i], y=ya+dy[i];
            if(x<0||x>=n||y<0||y>=m){
                continue;
            }
            if(g[x][y]!='.'){
                continue;
            }
            if(st[x][y]){
                continue;
            }
            cnt+=dfs(x, y);
        }
        return cnt;
    }
    signed main(){
        ios::sync_with_stdio(false);
        cin.tie(0);
        cout.tie(0);
        while(m=rd(), n=rd()){
            rep(i, 0, n){
                scanf("%s", g[i]);
            }
            int x, y;
            bool find=false;
            rep(i, 0, n){
                rep(j, 0, m){
                    if(g[i][j]=='@'){
                        x=i;
                        y=j;
                        find=true;
                        break;
                    }
                }
                if(find){
                    break;        
                }
            }
            memset(st, false, sizeof st);
            printf("%lld\n", dfs(x, y));
        }
        return 0;
    }

参考文献  
[AcWing 1113. 红与黑（算法提高课）y总视频][AcWing 1113. _y]

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![在这里插入图片描述][9cb4cb80a18345158f8a69e2f196e5b9.png]

[AcWing 1113.]: https://www.acwing.com/problem/content/1115/
[c7f4b951cf2f43b18d87ef29affe42b1.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/eb6580652c544aaaa5bee899d76a5ba9.png
[AcWing 1113. _y]: https://www.acwing.com/video/474/
[9cb4cb80a18345158f8a69e2f196e5b9.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/d17497c7449640b591626e650c360347.png