LeetCode Max Area of Island Solution Explained - Java

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[_ParijatChatterjee]

instead of that extra seen boolean, before the return statement in the area function just write grid[r][c] = 0.

[juanvibeats]

Here's an optimized version in JavaScript, instead of having the seen global variable, we can simply set the 1s equal to 0 once we've viewed them. Got the idea from Nick's video on 'Number of Islands' leetcode problem:

/**
* @param {number[][]} grid
* @return {number}
*/
var maxAreaOfIsland = function(grid) {
let maxArea = 0;

for(let i = 0; i < grid.length; i++) {
for(let j = 0; j < grid[0].length;j++) {
if(grid[i][j] === 1) {
let areaOfIsland = dfs(grid, i, j);
if(areaOfIsland > maxArea) {
maxArea = areaOfIsland;
}
}
}
}

return maxArea;
};

const dfs = (matrix, i, j, area) => {
if(i < 0 || j < 0 || i >= matrix.length || j >= matrix[0].length || matrix[i][j] === 0) {
return 0;
}
if(!area) area = 1;
area += 1;
matrix[i][j] = 0;

let up = dfs(matrix, i - 1, j, area);
let down = dfs(matrix, i + 1, j, area);
let left = dfs(matrix, i, j - 1, area);
let right = dfs(matrix, i, j + 1, area);

return 1 + up + down + right + left;
}

[vikrant]

Hey Nick, did you study any other questions too for your tech interviews. If you can share complete list you solved before interview that would be great!

[lifehacks]

could u pls upload word ladder 2 problem

[joecamroberon]

Can you explain why you are returning 1 + the recursive call?

[vishaldhanani]

It is not working in the test case of

[[0], [1]]. Please explain it. Thanks

[ZEEEDgenx]

Just to check if I'm understanding, we should return 0 on a seen island because, if we don't and we keep recursively visiting that island our area for the max area would go to infinity because it keeps checking its neighbor and its neighbor keeps checking it.

[msantagiulianab]

"Time Limit Exceeded", time-complexity is too high.