Detect Number of Islands - LeetCode - Go

main.go

package main

import "fmt"

func main() {
	var a = [][]int{
		{0, 0, 1, 1, 0},
		{0, 0, 1, 1, 0},
		{1, 0, 1, 0, 0},
		{1, 0, 1, 0, 0},
	}
	
	fmt.Println("Number of islands:", numIslands(a))
}

func markCurrentIsland(grid [][]int, x int, y int, r int, c int) {
	if x < 0 || x >= r || y < 0 || y >= c || grid[x][y] != 1 { // Boundary case for matrix
		return
	}

	// mark current cell as visited
	grid[x][y] = 2
	markCurrentIsland(grid, x+1, y, r, c) // Down
	markCurrentIsland(grid, x, y+1, r, c) // Right
	markCurrentIsland(grid, x-1, y, r, c) // Top
	markCurrentIsland(grid, x, y-1, r, c) // Left
}

func numIslands(grid [][]int) int {
	var i, j int

	var (
		noOfIslands = 0
		cols        = len(grid[0])
		rows        = len(grid)
	)

	if rows == 0 { // Empty grid boundary case
		return 0
	}

	// Iterate for all cells of the array
	for i = 0; i < rows; i++ {
		for j = 0; j < cols; j++ {
			if grid[i][j] == 1 {
				markCurrentIsland(grid, i, j, rows, cols)
				noOfIslands++
			}
		}
	}
	return noOfIslands
}