Add problem 200 - Number Of Islands

Author: anirudhology

problems/dfs/number_of_islands.go

@@ -0,0 +1,34 @@
+package dfs
+
+func NumberOfIslands(grid [][]byte) int {
+	// Special case
+	if len(grid) == 0 {
+		return 0
+	}
+	// Dimensions of the grid
+	m, n := len(grid), len(grid[0])
+	// Total number of islands
+	count := 0
+	// Process every cell in the grid
+	for i := 0; i < m; i++ {
+		for j := 0; j < n; j++ {
+			if grid[i][j] == '1' {
+				dfs(grid, i, j, m, n)
+				count++
+			}
+		}
+	}
+	return count
+}
+
+func dfs(grid [][]byte, i int, j int, m int, n int) {
+	// Base case
+	if i < 0 || i >= m || j < 0 || j >= n || grid[i][j] == '0' {
+		return
+	}
+	grid[i][j] = '0'
+	dfs(grid, i-1, j, m, n)
+	dfs(grid, i+1, j, m, n)
+	dfs(grid, i, j-1, m, n)
+	dfs(grid, i, j+1, m, n)
+}

tests/dynamic_programming/dfs/number_of_islands_test.go

@@ -0,0 +1,66 @@
+package dfs_test
+
+import (
+	"testing"
+
+	"github.com/anirudhology/leetcode-go/problems/dfs"
+)
+
+func TestNumIslands_EmptyGrid(t *testing.T) {
+	grid := [][]byte{}
+	if res := dfs.NumberOfIslands(grid); res != 0 {
+		t.Errorf("expected 0, got %d", res)
+	}
+}
+
+func TestNumIslands_NullGrid(t *testing.T) {
+	var grid [][]byte
+	if res := dfs.NumberOfIslands(grid); res != 0 {
+		t.Errorf("expected 0, got %d", res)
+	}
+}
+
+func TestNumIslands_SingleIsland(t *testing.T) {
+	grid := [][]byte{
+		{'1', '1', '0', '0'},
+		{'1', '1', '0', '0'},
+		{'0', '0', '0', '0'},
+		{'0', '0', '0', '0'},
+	}
+	if res := dfs.NumberOfIslands(grid); res != 1 {
+		t.Errorf("expected 1, got %d", res)
+	}
+}
+
+func TestNumIslands_MultipleIslands(t *testing.T) {
+	grid := [][]byte{
+		{'1', '1', '0', '0', '1'},
+		{'1', '0', '0', '1', '1'},
+		{'0', '0', '1', '0', '0'},
+		{'1', '0', '0', '1', '1'},
+	}
+	if res := dfs.NumberOfIslands(grid); res != 5 {
+		t.Errorf("expected 5, got %d", res)
+	}
+}
+
+func TestNumIslands_NoIslands(t *testing.T) {
+	grid := [][]byte{
+		{'0', '0', '0', '0'},
+		{'0', '0', '0', '0'},
+	}
+	if res := dfs.NumberOfIslands(grid); res != 0 {
+		t.Errorf("expected 0, got %d", res)
+	}
+}
+
+func TestNumIslands_MixedGrid(t *testing.T) {
+	grid := [][]byte{
+		{'1', '0', '1', '0'},
+		{'0', '1', '0', '1'},
+		{'1', '0', '1', '0'},
+	}
+	if res := dfs.NumberOfIslands(grid); res != 6 {
+		t.Errorf("expected 6, got %d", res)
+	}
+}