LeetCode 695. Max Area of Island

1、BFS

class Solution {
public:
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        int maxArea = 0, rows = grid.size(), columns = grid[0].size();
        for (int i = 0; i < rows; ++i) {
            for (int j = 0; j < columns; ++j) {
                if (grid[i][j] == 1) {
                    maxArea = max(maxArea,BFS(grid, i, j));
                }
            }
        }
        return maxArea;
    }
private:
    int BFS(vector<vector<int>>& grid, int row, int column){
        int rows = grid.size(), columns = grid[0].size(), ans = 1;
        queue<pair<int, int>> q;
        q.push({row,column});
        grid[row][column] = 2;
        vector<int> dir({0,1,0,-1,0});
        while (!q.empty()) {
            int r = q.front().first;
            int c = q.front().second;
            q.pop();
            for (int i = 0; i < 4; ++i) {
                int rr = r + dir[i];
                int cc = c + dir[i+1];
                if (0 <= rr && rr < rows && 0 <= cc && cc < columns && grid[rr][cc] == 1) {
                    ++ans;
                    q.push({rr,cc});
                    grid[rr][cc] = 2;
                }
            }
        }
        return ans;
    }
};