蓝桥杯题目:全球变暖

算法:广搜,c++队列
小知识点:坐标的变化

#include<bits/stdc++.h>
using namespace std;
const int N = 1010;
char mp[N][N];
int vis[N][N];
int d[4][2] = {{0,1}, {0,-1}, {1,0}, {-1,0}}; //四个方向
int flag;
void bfs(int x, int y) {
    queue<pair<int, int>> q;
    q.push({x, y});
    vis[x][y] = 1;      //标记这个'#'被搜过
    while (q.size()) {
        pair<int, int> t = q.front();
        q.pop();
        int tx = t.first, ty = t.second;
        if( mp[tx][ty+1]=='#' && mp[tx][ty-1]=='#' &&
            mp[tx+1][ty]=='#' && mp[tx-1][ty]=='#'   )
            flag = 1; //上下左右都是陆地，不会淹没
        for (int i = 0; i < 4; i++) {    //扩展(tx,ty)的4个邻居
            int nx = tx + d[i][0], ny = ty + d[i][1];
            if(vis[nx][ny]==0 && mp[nx][ny]=='#'){  //把陆地放进队列
                vis[nx][ny] = 1;  //注意：这一句必不可少
                q.push({nx, ny});
            }
        }
    }
}
int main() {
    int n;  cin >> n;
    for (int i = 0; i < n; i++)
        cin >> mp[i];
    int ans = 0;
    for (int i = 0; i < n; i++)
        for (int j = 0; j < n; j++)
            if (mp[i][j] == '#' && vis[i][j]==0) {
                flag = 0;
                bfs(i, j);
                if(flag == 0)  //这个岛全部被淹
                    ans++;     //统计岛的数量
            }
    cout << ans << endl;
    return 0;
}