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Arrays_Merge2SortedArrWithOutExtraSpace.java
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Arrays_Merge2SortedArrWithOutExtraSpace.java
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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
// https://practice.geeksforgeeks.org/problems/merge-two-sorted-arrays5135/1
// https://practice.geeksforgeeks.org/problems/merge-two-sorted-arrays-1587115620/1/
// https://www.youtube.com/watch?v=hVl2b3bLzBw&ab_channel=takeUforward (BEST VIDEO)
// https://www.youtube.com/watch?v=Bcay1cEqrrA&ab_channel=PawanGupta (A good video)
// https://www.geeksforgeeks.org/efficiently-merging-two-sorted-arrays-with-o1-extra-space/ (BEST Post <- I followed this)
// https://www.youtube.com/watch?v=9crZRd8GPWM&ab_channel=Jenny%27slecturesCS%2FITNET%26JRF (Shell Sort)
// https://www.geeksforgeeks.org/shellsort/
// https://www.youtube.com/watch?v=OGzPmgsI-pQ&ab_channel=GeeksforGeeks (Insertion Sort)
/* Intuition behind the logic is Shell sort */
public class Arrays_Merge2SortedArrWithOutExtraSpace {
/* time complexity : O((n + m) * log(n + m)) , space complexity : O(1) */
private static void mergeTwoSortedArraysWithoutExtraSpace(int[] array1, int[] array2, int n, int m) {
int i = 0;
int j = 0;
int totalSize = n + m;
for (int gap = nextGap(totalSize) ; gap > 0; gap = nextGap(gap)) {
/* comparing elements in the first array */
for (i = 0; i + gap < n; i++) {
if (array1[i] > array1[i + gap]) {
swap(array1, array1, i, i + gap);
}
}
/* comparing elements in both the arrays */
for (j = (gap > n ? gap - n : 0); (i < n && j < m); i++, j++) {
if (array1[i] > array2[j]) {
swap(array1, array2, i, j);
}
}
if (j < m) {
/* comparing elements in the second array */
for (j = 0; j + gap < m; j++) {
if (array2[j] > array2[j + gap]) {
swap(array2, array2, j, j + gap);
}
}
}
}
}
private static void swap(int[] array1, int[] array2, int i, int j) {
int temp = array1[i];
array1[i] = array2[j];
array2[j] = temp;
}
private static int nextGap(int gap) {
if (gap <= 1) return 0;
return (gap / 2) + (gap % 2); /* We are taking the ceiling value */
}
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int t = Integer.parseInt(br.readLine().trim());
while (t -- > 0) {
String[] nm = br.readLine().trim().split("\\s+");
int n = Integer.parseInt(nm[0]);
int m = Integer.parseInt(nm[1]);
String[] input1 = br.readLine().trim().split("\\s+");
String[] input2 = br.readLine().trim().split("\\s+");
int[] array1 = new int[n];
int[] array2 = new int[m];
for (int i = 0; i < n; i++) {
array1[i] = Integer.parseInt(input1[i]);
}
for (int i = 0; i < m; i++) {
array2[i] = Integer.parseInt(input2[i]);
}
mergeTwoSortedArraysWithoutExtraSpace(array1, array2, n, m);
print(array1, array2, n, m);
}
}
private static void print(int[] array1, int[] array2, int n, int m) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < n; i++) {
sb.append(array1[i]).append(" ");
}
for (int j = 0; j < m; j++) {
sb.append(array2[j]).append(" ");
}
System.out.println(sb);
sb.setLength(0);
}
/*
* 10 10
* 7 9 9 10 11 11 13 14 17 19
* 1 1 4 5 8 11 13 16 19 19
*
* Its Correct output is: 1 1 4 5 7 8 9 9 10 11 11 11 13 13 14 16 17 19 19 19
* And Your Code's output is: 1 1 4 5 7 8 9 9 10 11 11 13 11 13 14 16 17 19 19 19
*
* 5 5
* 1 3 5 7 10
* 0 2 6 8 9
*
* */
/* SHELL SORT ALGORITHM
for (int gap = N / 2; gap >= 1; gap / 2) {
for (int j = gap; j < N; j++) {
for (int i = j - gap; i >= 0; i - gap) {
if (arr[i] < arr[i + gap]) {
break;
}
else {
swap(arr[i], arr[i + gap]);
}
}
}
}
time complexity depends upon the gap sequence.
here we are taking the gap sequence as N / 2.
so time complexity : O(N^2)
space complexity : O(1)
*/
}