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QueueReverser.java
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QueueReverser.java
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package com.faisal;
import java.util.Queue;
import java.util.Stack;
public class QueueReverser {
public static void reverse(Queue<Integer> queue, int k) {
if (k < 0 || k > queue.size())
throw new IllegalArgumentException();
java.util.Stack<Integer> stack = new Stack<>();
// Dequeue the first K elements from the queue
// and push them onto the stack
for (int i = 0; i < k; i++)
stack.push(queue.remove());
// Enqueue the content of the stack at the
// back of the queue
while (!stack.empty())
queue.add(stack.pop());
// Add the remaining items in the queue (items
// after the first K elements) to the back of the
// queue and remove them from the beginning of the queue
for (int i = 0; i < queue.size() - k; i++)
queue.add(queue.remove());
}
}