Merge pull request #568 from priyashuu/SpiralMatrix2

Add Java solution for Spiral Matrix II problem

Author: Pradeepsingh61

Java/algorithms/arrays/SpiralMatrixII.java

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+/*
+ * Algorithm Name:Spiral Matrix2 .
+ * Programming Language: Java
+ * Category: Array ,matrix
+ * Difficulty Level: Medium
+ *
+ * Author: Priya Rani 
+ *
+ * Algorithm Description: Given a positive integer n, generate an n x n matrix filled with elements from 1 to n2 in spiral order.
+ * Input: n = 3
+   Output: [[1,2,3],[8,9,4],[7,6,5]]
+   Example 2:
+   Input: n = 1
+   Output: [[1]]
+
+ 
+
+ * Time Complexity: O(1) Time complexity: O(n²)
+ * Space complexity: O(1) (excluding output matrix)
+*/
+import java.util.*;
+
+public class SpiralMatrixII {
+    public int[][] generateMatrix(int n) {
+        int[][] matrix = new int[n][n];
+        int left = 0, right = n - 1;
+        int top = 0, bottom = n - 1;
+        int num = 1;
+
+        while (left <= right && top <= bottom) {
+            for (int i = left; i <= right; i++) {
+                matrix[top][i] = num++;
+            }
+            top++;
+
+            for (int i = top; i <= bottom; i++) {
+                matrix[i][right] = num++;
+            }
+            right--;
+
+            if (top <= bottom) {
+                for (int i = right; i >= left; i--) {
+                    matrix[bottom][i] = num++;
+                }
+                bottom--;
+            }
+
+            if (left <= right) {
+                for (int i = bottom; i >= top; i--) {
+                    matrix[i][left] = num++;
+                }
+                left++;
+            }
+        }
+
+        return matrix;
+    }
+
+    public static void main(String[] args) {
+        SpiralMatrixII sm = new SpiralMatrixII();
+        int n = 3;
+        int[][] result = sm.generateMatrix(n);
+
+        for (int[] row : result) {
+            System.out.println(Arrays.toString(row));
+        }
+    }
+}
+