[LeetCode/JavaScript] 695. Max Area of Island (medium)

 

문제 

You are given an m x n binary matrix grid. An island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.

The area of an island is the number of cells with a value 1 in the island.

Return the maximum area of an island in grid. If there is no island, return 0.

 

 

입출력

Example 1:

Input: grid = [[0,0,1,0,0,0,0,1,0,0,0,0,0],[0,0,0,0,0,0,0,1,1,1,0,0,0],[0,1,1,0,1,0,0,0,0,0,0,0,0],[0,1,0,0,1,1,0,0,1,0,1,0,0],[0,1,0,0,1,1,0,0,1,1,1,0,0],[0,0,0,0,0,0,0,0,0,0,1,0,0],[0,0,0,0,0,0,0,1,1,1,0,0,0],[0,0,0,0,0,0,0,1,1,0,0,0,0]]
Output: 6
Explanation: The answer is not 11, because the island must be connected 4-directionally.

 

Example 2:

Input: grid = [[0,0,0,0,0,0,0,0]]
Output: 0

 

 

제약

Constraints:

• m == grid.length
• n == grid[i].length
• 1 <= m, n <= 50
• grid[i][j] is either 0 or 1.

 

 

코드

var area;

var maxAreaOfIsland = function(grid) {
    let maxArea = 0;
    
    for(let i=0; i<grid.length; i++) {
        for(let j=0; j!=-1 && j<=grid[0].length;) {
            area = 0;
            j = (j===0) ? grid[i].indexOf(1) : grid[i].indexOf(1, j+1);
            
            if(grid[i][j]==1) {
                isConnected(i, j, grid);
                if(area > maxArea) maxArea = area;
            }
        }
    }
    return maxArea;
};

function isConnected(row, col, grid) {
    grid[row][col] = -1; 
    area++;
    
    if(row-1>=0 && grid[row-1][col]==1) isConnected(row-1, col, grid);
    if(row+1<grid.length && grid[row+1][col]==1) isConnected(row+1, col, grid);
    if(col-1>=0 && grid[row][col-1]==1) isConnected(row, col-1, grid);
    if(col+1<grid[0].length && grid[row][col+1]==1) isConnected(row, col+1, grid);
}