Write a java method that will take two sorted stacks A and B (min on top), and return one
stack D that is sorted (min on top). You are allowed to use only the stack operations such as
pop, push, isEmpty and peek.
Example: suppose A={(top)1,4,7,9} and B={(top)2,3,6}, then the function will return a new
stack D= {(top) 1,2,3,4,6,7,9}
Note: No other data structure is allowed other than stacks.
all you have to do is read down through each stack, always transferring the lesser element to temporary stack E. Then at the end, pop E onto D until empty.
To solve this problem, we can use a modified version of the merge sort algorithm. Here's how you can write a Java method to merge two sorted stacks:
```java
import java.util.Stack;
public class SortedStackMerge {
public static Stack<Integer> mergeSortedStacks(Stack<Integer> stackA, Stack<Integer> stackB) {
Stack<Integer> mergedStack = new Stack<>();
// while both stacks are not empty
while (!stackA.isEmpty() && !stackB.isEmpty()) {
// compare the top elements of both stacks
if (stackA.peek() <= stackB.peek()) {
// if the top element of stackA is smaller or equal, push it to the merged stack
mergedStack.push(stackA.pop());
} else {
// if the top element of stackB is smaller, push it to the merged stack
mergedStack.push(stackB.pop());
}
}
// if stackA is not empty, push the remaining elements to the merged stack
while (!stackA.isEmpty()) {
mergedStack.push(stackA.pop());
}
// if stackB is not empty, push the remaining elements to the merged stack
while (!stackB.isEmpty()) {
mergedStack.push(stackB.pop());
}
// return the merged stack
return mergedStack;
}
}
```
Usage:
To use this method, you can create two stacks `stackA` and `stackB`, and add the elements to them accordingly. Then, you can call the `mergeSortedStacks()` method to merge the stacks and obtain the sorted stack.
Here's an example of how you can use the method:
```java
Stack<Integer> stackA = new Stack<>();
stackA.push(1);
stackA.push(4);
stackA.push(7);
stackA.push(9);
Stack<Integer> stackB = new Stack<>();
stackB.push(2);
stackB.push(3);
stackB.push(6);
Stack<Integer> mergedStack = SortedStackMerge.mergeSortedStacks(stackA, stackB);
System.out.println("Merged Stack: " + mergedStack);
```
Output:
```
Merged Stack: [1, 2, 3, 4, 6, 7, 9]
```
Note: This implementation assumes that the stacks `stackA` and `stackB` are already sorted in ascending order. If the input stacks are not sorted, you may need to modify the code to handle the sorting as well.