Adding spiral_matrix implemetation and explain it

Author: SubhadipD9

data_structures/arrays/spiral_matrix.py

@@ -1,48 +1,65 @@
 class Solution:
     def generateMatrix(self, n: int) -> list[list[int]]:
+        # Create an n x n matrix filled with zeros
         result = [[0] * n for _ in range(n)]
+        
+        # Start filling numbers from 1 to n^2
         value = 1
 
-        colStart, colEnd = 0, n - 1
+        # Define the boundaries for rows and columns
         rowStart, rowEnd = 0, n - 1
+        colStart, colEnd = 0, n - 1
 
-        while colStart <= colEnd and rowStart <= rowEnd:
-            # Left to Right
+        # Continue filling the matrix layer by layer in spiral order
+        while rowStart <= rowEnd and colStart <= colEnd:
+            
+            # Step 1: Fill the top row (left → right)
             for i in range(colStart, colEnd + 1):
-                result[rowStart][i] = value
-                value += 1
-            rowStart += 1
+                result[rowStart][i] = value   # assign the current value
+                value += 1                    # move to next number
+            rowStart += 1  # move top boundary down (row filled)
 
-            # Up to Down
+            # Step 2: Fill the rightmost column (top → bottom)
             for j in range(rowStart, rowEnd + 1):
                 result[j][colEnd] = value
                 value += 1
-            colEnd -= 1
+            colEnd -= 1  # move right boundary left (column filled)
 
-            # Right to Left
+            # Step 3: Fill the bottom row (right → left)
+            # Only if there are rows remaining to fill
             if rowStart <= rowEnd:
                 for k in range(colEnd, colStart - 1, -1):
                     result[rowEnd][k] = value
                     value += 1
-                rowEnd -= 1
+                rowEnd -= 1  # move bottom boundary up (row filled)
 
-            # Down to Up
+            # Step 4: Fill the leftmost column (bottom → top)
+            # Only if there are columns remaining to fill
             if colStart <= colEnd:
                 for l in range(rowEnd, rowStart - 1, -1):
                     result[l][colStart] = value
                     value += 1
-                colStart += 1
+                colStart += 1  # move left boundary right (column filled)
 
+        # Return the completed spiral matrix
         return result
 
 
-# Test
+# Example usage:
 solution = Solution()
 
-n = 3
-
+n = 3  # You can change this to any number, e.g. 4 or 5
 matrix = solution.generateMatrix(n)
 
-# Print the matrix
+# Print the spiral matrix row by row
 for row in matrix:
     print(row)
+
+
+# Output: 
+'''
+    [1, 2, 3]
+    [8, 9, 4]
+    [7, 6, 5]
+
+'''