题解 | 岛屿数量

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
#define quick ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
const int inf = 0x3f3f3f3f, maxn = 2e5 + 5, mod = 998252334;
inline int read() {
    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;
}
int dx[]={1,-1,1,-1,0, 0, 1,-1};
int dy[]={0, 0,1,-1,1,-1,-1, 1};
int n,m;
void dfs(int x,int y,vector<vector<int>>&grid){
    for(int i=0;i<8;i++){
        int nx=x+dx[i];
        int ny=y+dy[i];
        if(nx<1||ny<1||nx>n||ny>m) continue;
        if(grid[nx][ny]==2||grid[nx][ny]==0) continue;
        if(grid[nx][ny]==1){
            grid[nx][ny]=2;
            dfs(nx,ny,grid);
        }
    }
}
void solve() {
    n=read();m=read();
    vector<vector<int>>grid(n+1,vector<int>(m+1));
    char k;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            cin>>k;
            if(k=='W') grid[i][j]=1;
            else if(k=='.') grid[i][j]=0;
        }
    }

    int ans=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            if(grid[i][j]==1){
                dfs(i,j,grid);
                ans++;
            }
        }
    }
    cout<<ans<<endl;
}
signed main() {
    int t = 1;
//  cin>>t;
    while (t--) {
        solve();
    }
    return 0;
}