Sword finger offer II 105 Maximum area of the island

The finger of the sword Offer II 105. The largest area of the island 【 Medium question 】

Ideas ：【DFS】

Every time I meet an island , Record the number of islands as 1, At the same time, take this island as the center, search the adjacent islands in four directions up, down, left and right, and record the number of islands , At the same time, the island was sunk ( Set as 0), Indicates that it has been searched .

When an island is searched in four directions , Update the maximum number of islands , Because each island has the same area , So the largest number of islands is the largest island area .

Code ：

class Solution {
    

    static int m;
    static int n;

    public int maxAreaOfIsland(int[][] grid) {
    
        m = grid.length;
        n = grid[0].length;
        int ans = 0;
        for (int i = 0; i < m; i++) {
    
            for (int j = 0; j < n; j++) {
    
                if (grid[i][j] != 0){
    
                    ans = Math.max(ans,dfs(i,j,grid));
                }
            }
        }
        return ans;
    }

    public int dfs(int x,int y,int[][] grid){
    
        if (x < 0 || y < 0 || x == m || y == n || grid[x][y] == 0){
    
            return 0;
        }
        grid[x][y] = 0;
        int[][] f = {
    {
    0,1},{
    0,-1},{
    -1,0},{
    1,0}};
        int cnt = 1;
        for (int i = 0; i < 4; i++) {
    
            int dx = x + f[i][0],dy = y + f[i][1];
            cnt += dfs(dx,dy,grid);
        }
        return cnt;
    }
}