https://leetcode.com/problems/construct-quad-tree/

Author: harshitgindra

LeetCodeSolutions/DivideAndConquer/ConstructQuadTree.cs

@@ -0,0 +1,81 @@
+namespace LeetCodeSolutions.DivideAndConquer;
+
+/// <summary>
+/// https://leetcode.com/problems/construct-quad-tree/
+/// </summary>
+public class ConstructQuadTree
+{
+    public Node Construct(int[][] grid)
+    {
+        // Start the recursive construction from the entire grid
+        return Construct(grid, 0, 0, grid.Length);
+    }
+
+    public Node Construct(int[][] grid, int i, int j, int length)
+    {
+        // Check if the current section has all the same values
+        if (IsSame(grid, i, j, length))
+        {
+            // Create a leaf node with the value of the first cell in this section
+            return new Node(grid[i][j] == 1, true);
+        }
+        else
+        {
+            // Create a non-leaf node
+            Node node = new Node(false, false);
+
+            // Divide the current section into four quadrants and construct nodes for each
+            int halfLength = length / 2;
+            node.topLeft = Construct(grid, i, j, halfLength);
+            node.topRight = Construct(grid, i, j + halfLength, halfLength);
+            node.bottomLeft = Construct(grid, i + halfLength, j, halfLength);
+            node.bottomRight = Construct(grid, i + halfLength, j + halfLength, halfLength);
+
+            return node;
+        }
+    }
+    private bool IsSame(int[][] grid, int row, int column, int length)
+    {
+        // Get the value of the first cell to compare against
+        int value = grid[row][column];
+
+        // Check every cell in the section
+        for (int i = row; i < row + length; i++)
+        {
+            for (int j = column; j < column + length; j++)
+            {
+                // If any cell has a different value, return false
+                if (grid[i][j] != value)
+                {
+                    return false;
+                }
+            }
+        }
+
+        // All cells have the same value
+        return true;
+    }
+}
+
+/// <summary>
+/// Definition for a Quadtree node.
+/// </summary>
+public class Node
+{
+    public bool val;
+    public bool isLeaf;
+    public Node topLeft;
+    public Node topRight;
+    public Node bottomLeft;
+    public Node bottomRight;
+
+    public Node(bool _val = false, bool _isLeaf = false)
+    {
+        val = _val;
+        isLeaf = _isLeaf;
+        topLeft = null;
+        topRight = null;
+        bottomLeft = null;
+        bottomRight = null;
+    }
+}

README.md

@@ -168,7 +168,7 @@ The Top Interview 150 collection on Leetcode is a curated set of 150 interview q
 | <br>        Divide &amp; Conquer<br>         |                                                                                                           |            |        |
 | 108                                          | Convert Sorted Array to Binary Search Tree                                                                | Easy       |   ✅     |
 | 109                                          | Sort List                                                                                                 | Medium     |   ✅     |
-| 110                                          | Construct Quad Tree                                                                                       | Medium     |        |
+| 110                                          | Construct Quad Tree                                                                                       | Medium     |   ✅     |
 | 111                                          | Merge k Sorted Lists                                                                                      | Hard       |   ✅     |
 | <br>        Kadane&#39;s Algorithm<br>       |                                                                                                           |            |        |
 | 112                                          | Maximum Subarray                                                                                          | Medium     |        |