https://leetcode.com/problems/number-of-islands/

Author: harshitgindra

LeetCodeSolutions/Graph/NumberOfIslands.cs

@@ -0,0 +1,73 @@
+namespace LeetCodeSolutions.Graph
+{
+    public class NumberOfIslands
+    {
+        public int NumIslands(char[][] grid)
+        {
+            int islandCount = 0;
+            int rows = grid.Length;
+            int cols = grid[0].Length;
+
+            // Iterate through each cell in the grid
+            for (int row = 0; row < rows; row++)
+            {
+                for (int col = 0; col < cols; col++)
+                {
+                    // When we find a land cell ('1'), explore the entire island
+                    if (grid[row][col] == '1')
+                    {
+                        islandCount++;
+                        ExploreIsland(grid, row, col);
+                    }
+                }
+            }
+
+            return islandCount;
+        }
+
+        private void ExploreIsland(char[][] grid, int row, int col)
+        {
+            int rows = grid.Length;
+            int cols = grid[0].Length;
+
+            // Check boundary conditions and if current cell is land
+            if (row < 0 || col < 0 || row >= rows || col >= cols || grid[row][col] == '0')
+            {
+                return;
+            }
+
+            // Mark current cell as visited
+            grid[row][col] = '0';
+
+            // Explore in all four directions (up, right, down, left)
+            ExploreIsland(grid, row + 1, col); // Down
+            ExploreIsland(grid, row - 1, col); // Up
+            ExploreIsland(grid, row, col + 1); // Right
+            ExploreIsland(grid, row, col - 1); // Left
+        }
+
+        [Test(Description = "https://leetcode.com/problems/number-of-islands/")]
+        [Category("Medium")]
+        [Category("LeetCode")]
+        [Category("Number of Islands")]
+        [TestCaseSource(nameof(Input))]
+        [Category("Graph")]
+        [Category("TopInterview")]
+        public void Test1((int Output, char[][] Input) item)
+        {
+            var response = this.NumIslands(item.Input);
+            Assert.That(response, Is.EqualTo(item.Output));
+        }
+
+        public static IEnumerable<(int Output, char[][] Input)> Input =>
+            new List<(int Output, char[][] Input)>()
+            {
+                (1, [
+                    ['1', '1', '1', '1', '0'],
+                    ['1', '1', '0', '1', '0'],
+                    ['1', '1', '0', '0', '0'],
+                    ['0', '0', '0', '0', '0']
+                ])
+            };
+    }
+}

LeetCodeSolutions/LeetCodeSolutions.csproj

@@ -15,7 +15,6 @@
  <ItemGroup>
    <Folder Include="Backtracking\" />
    <Folder Include="GraphBfs\" />
-   <Folder Include="Graph\" />
    <Folder Include="Heap\" />
    <Folder Include="Intervals\" />
    <Folder Include="KadaneAlgorithm\" />

README.md

@@ -143,7 +143,7 @@ The Top Interview 150 collection on Leetcode is a curated set of 150 interview q
 | 87                                           | Kth Smallest Element in a BST                                                                             | Medium     |        |
 | 98                                           | Validate Binary Search Tree                                                                               | Medium     |   ✅     |
 | <br>        Graph General<br>                |                                                                                                           |            |        |
-| 89                                           | Number of Islands                                                                                         | Medium     |        |
+| 89                                           | Number of Islands                                                                                         | Medium     |   ✅     |
 | 90                                           | Surrounded Regions                                                                                        | Medium     |        |
 | 91                                           | Clone Graph                                                                                               | Medium     |        |
 | 92                                           | Evaluate Division                                                                                         | Medium     |        |