chore(Java): add merge without extra space for two array (#592)

algorithms/Java/README.md

@@ -10,6 +10,7 @@
 - [K-th Element of Two Sorted Arrays](arrays/kth-element--orted-array.java)
 - [Trapping Rain Water](arrays/trapping-rain-water.java)
 - [Ugly Number](arrays/ugly-number.java)
+- [Merge Without Extra Space](arrays/merge-without-extra-space.java)
 
 ## Graphs
 - [Dijkstras](graphs/Dijkstras.java)

algorithms/Java/arrays/merge-without-extra-space.java

@@ -0,0 +1,95 @@
+// Program to merge two sorted arrays without any extra space in Java
+/*
+Author : Suraj Kumar Modi
+Github : https://github.com/skmodi649
+ */
+
+
+/** Algorithm :
+ * 1) Initialize i,j as n-1,0 where n is size of arr1
+ * 2) Iterate through every element of arr1 and arr2 using two pointers i and j respectively
+ *   while(i>=0 && j<m)
+ *     if arr1[i] is more than arr2[j]
+ *         swap arr1[i] and arr2[j]
+ *     else
+ *         decrement i
+ *         increment j
+ *
+ * 3) Sort both arr1 and arr2
+ */
+
+import java.util.*;
+
+class MergingWithoutExtraSpace {
+    // Driver code
+    public static void main(String[] args) {
+
+            Scanner sc = new Scanner(System.in);
+            System.out.println("Enter the sizes of arr1 and arr2  respectively : ");
+            int n = sc.nextInt();
+            int m = sc.nextInt();
+            int[] arr1 = new int[n];
+            int[] arr2 = new int[m];
+            System.out.println("Enter elements in the arr1 : ");
+            for (int i = 0; i < n; i++) {
+                arr1[i] = sc.nextInt();
+            }
+            System.out.println("Enter elements in the arr2 : ");
+            for (int i = 0; i < m; i++) {
+                arr2[i] = sc.nextInt();
+            }
+
+            System.out.println("Merged array : ");
+        MergingWithoutExtraSpace ob = new MergingWithoutExtraSpace();
+            ob.merge(arr1 , arr2 , n , m);
+
+            StringBuffer str = new StringBuffer();
+            for (int i = 0; i < n; i++) {
+                str.append(arr1[i]).append(" ");
+            }
+            for (int i = 0; i < m; i++) {
+                str.append(arr2[i]).append(" ");
+            }
+            System.out.println(str);
+        }
+
+    public void merge(int[] arr1, int[] arr2, int n, int m) {
+        int i = n-1 , j = 0;
+        while(i>=0 && j<m)
+        {
+            if(arr1[i] > arr2[j])
+            {
+                int temp = arr1[i];
+                arr1[i] = arr2[j];
+                arr2[j] = temp;
+            }
+            i--;
+            j++;
+        }
+        Arrays.sort(arr1);
+        Arrays.sort(arr2);
+    }
+}
+
+
+/** TEST CASES :
+ *
+ * Test Case 1 :
+ * Input : n = 3 , m = 4
+ * arr1[] = {1,27,36}    arr2[] = {12,14,16,22}
+ * Output :
+ * 1 12 14 16 22 27 36
+ *
+ * Test Case 2 :
+ * Input : n = 4 , m = 5
+ * arr1[] = {0,12,21,27}    arr2[] = {4,6,8,10,12}
+ * Output :
+ * 0 4 6 8 10 12 12 21 27
+ */
+
+/**
+ * Time Complexity : O((n+m)log(n+m))
+ * Auxiliary Space Complexity : O(1)
+ */
+
+