[LeetCode] 695. The maximum area of the island (DFS / BFS)

topic

Given a two-dimensional array of non-null grid number 0 and 1, is an island formed of a combination of four directions (horizontal or vertical) 1 (representing the land). You can assume that the four edges of the two-dimensional matrix are surrounded by water.

Find a given two-dimensional array in the largest island in the area. (If there are no islands, the area is returned to 0.)

answer

dis / bfs bare bare bare title.
Their search practice too little, he wanted more practice!

all

bfs version

Code (dfs)

class Solution {
    public int maxAreaOfIsland(int[][] grid) {
        int maxArea=0;
        
        if(grid==null){
            return 0;
        }
        
        for(int i=0;i<grid.length;++i){
            for(int j=0;j<grid[0].length;++j){
                if(grid[i][j]==1){
                    int area=dfs(grid,i,j);
                    maxArea=area>maxArea?area:maxArea;
                }
            }
        }
        return maxArea;
    }
    
    public int dfs(int[][] grid,int i,int j){
        int area=1;
        grid[i][j]=0;
        int[] dx={0,0,-1,1};
        int[] dy={-1,1,0,0};
        for(int m=0;m<4;++m){
            if(vaild(grid,i+dx[m],j+dy[m])&&grid[i+dx[m]][j+dy[m]]==1){
                area+=dfs(grid,i+dx[m],j+dy[m]);
            }
        }
        return area;
    }
    
    public boolean vaild(int[][] grid,int i,int j){
        return i>=0&&i<grid.length&&j>=0&&j<grid[0].length;
    }
}