Find max area island in Matrix

max-area-island-matrix.java

class Solution {
    public int maxAreaOfIsland(int[][] matrix) {
        int rows = matrix.length;
        int cols = matrix[0].length;
        // return if empty matrix
        if (cols == 0) return 0;

        int[][] visited = new int[rows][cols];
        int maxArea = 0;

        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                // if value is 1 and not visited
                if (matrix[i][j] == 1 && visited[i][j] == 0) {
                    int area = dfs(matrix, i, j, visited);
                    maxArea = Math.max(area, maxArea);
                }
            }
        }
        return maxArea;
    }
    
    private int dfs(int[][] matrix, int row, int col, int[][] visited) {
        if ((row < 0 || row >= matrix.length) || (col < 0 || col >= matrix[0].length)) return 0;
        if (visited[row][col] == 1) return 0;
        if (matrix[row][col] == 0) return 0;
        visited[row][col] = 1;
        return 1 +
            dfs(matrix, row, col - 1, visited) +
            dfs(matrix, row - 1, col, visited) +
            dfs(matrix, row, col + 1, visited) +
            dfs(matrix, row + 1, col, visited);
    }
}