solves spiral matrix ii

Author: anishLearnsToCode

README.md

@@ -57,6 +57,7 @@
 |  56  | [Merge Intervals](https://leetcode.com/problems/merge-intervals)                                                                                          |                                                                 [![Java](assets/java.png)](src/MergeIntervals.java)                                                                  |                                                                                                                                   |
 |  57  | [Insert Interval](https://leetcode.com/problems/insert-interval)                                                                                          |                                                                 [![Java](assets/java.png)](src/InsertInterval.java)                                                                  |                                                                                                                                   |
 |  58  | [Length of Last Word](https://leetcode.com/problems/length-of-last-word)                                                                                  |                                 [![Java](assets/java.png)](src/LengthOfLastWord.java) [![Python](assets/python.png)](python/length_of_last_word.py)                                  |                                                                                                                                   |
+|  59  | [Spiral Matrix II](https://leetcode.com/problems/spiral-matrix-ii)                                                                                        |                                                                 [![Java](assets/java.png)](src/SpiralMatrixII.java)                                                                  |                                                                                                                                   |
 |  66  | [Plus One](https://leetcode.com/problems/plus-one)                                                                                                        |                                           [![Java](assets/java.png)](src/PlusOne.java) [![Python](assets/python.png)](python/plus_one.py)                                            |                                                                                                                                   |
 |  67  | [Add Binary](https://leetcode.com/problems/add-binary)                                                                                                    |                                         [![Java](assets/java.png)](src/AddBinary.java) [![Python](assets/python.png)](python/add_binary.py)                                          |                                                                                                                                   |
 |  69  | [Sqrt(x)](https://leetcode.com/problems/sqrtx)                                                                                                            |                                              [![Java](assets/java.png)](src/Sqrtx.java) [![Python](assets/python.png)](python/sqrt.py)                                               |                                                                                                                                   |

src/SpiralMatrixII.java

@@ -0,0 +1,34 @@
+// https://leetcode.com/problems/spiral-matrix-ii
+// T: O(n^2)
+// S: O(n^2)
+
+public class SpiralMatrixII {
+  public int[][] generateMatrix(int n) {
+    final int[][] matrix = new int[n][n];
+    final int rows = matrix.length, columns = matrix[0].length, elements = rows * columns;
+
+    for (int i = 0, top = 0, bottom = rows, left = 0, right = columns, k = 1 ; ; ) {
+      for (int row = top, column = left ; column < right ; column++, i++) {
+        matrix[row][column] = k++;
+      }
+      top++;
+      if (i == elements) break;
+      for (int row = top, column = right - 1 ; row < bottom ; row++, i++) {
+        matrix[row][column] = k++;
+      }
+      right--;
+      if (i == elements) break;
+      for (int row = bottom - 1, column = right - 1 ; column >= left ; column--, i++) {
+        matrix[row][column] = k++;
+      }
+      bottom--;
+      if (i == elements) break;
+      for (int row = bottom - 1, column = left ; row >= top ; row--, i++) {
+        matrix[row][column] = k++;
+      }
+      left++;
+      if (i == elements) break;
+    }
+    return matrix;
+  }
+}