将队列的前半部分与后半部分交错

给定一个偶数长度的整数队列，通过将队列的前半部分与队列的后半部分交错来重新排列元素。我们只能使用队列数据结构。
例子：

Input :  1 2 3 4
Output : 1 3 2 4

Input : 11 12 13 14 15 16 17 18 19 20
Output : 11 16 12 17 13 18 14 19 15 20

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创建两个辅助队列 q1 和 q2。将前半部分插入一个队列 q1，另一半插入另一个队列 q2。现在通过交替从 q1 和 q2 中选取元素将元素插入给定队列。

CPP

// CPP program to interleave queue elements
// using only queue data structure.
#include 
using namespace std;
 
void interleave(queue &q)
{
    queue q1, q2;
 
    int n = q.size();
 
    // Insert first half in q1
    for (int i = 0; i < n / 2; i++) {
        q1.push(q.front());
        q.pop();
    }
 
    // insert second half in q2
    for (int i = 0; i < n / 2; i++) {
        q2.push(q.front());
        q.pop();
    }
    
    // Insert elements of q1 and q2 back
    // to q in alternate order.
    for (int i = 0; i < n/2; i++) {
        q.push(q1.front());
        q1.pop();
        q.push(q2.front());
        q2.pop();
    }
}
 
// Driver code
int main()
{
    // Creating an example queue with 10
    // elements.
    queue q;
    for (int i = 1; i <= 10; i++)
        q.push(i); 
 
    interleave(q);
 
    // Printing queue elements
    int n = q.size();
    for (int i = 0; i < n; i++) {
        cout << q.front() << " ";
        q.pop();
    }
}

Java

// Java program to interleave queue elements
// using only queue data structure.
import java.util.LinkedList;
import java.util.Queue;
 
public class GFG {
 
    static void interleave(Queue q)
    {
        Queue q1, q2;
        q1 = new LinkedList();
        q2 = new LinkedList();
 
        int n = q.size();
 
        // Insert first half in q1
        for (int i = 0; i < n / 2; i++) {
            q1.add(q.peek());
            q.poll();
        }
 
        // insert second half in q2
        for (int i = 0; i < n / 2; i++) {
            q2.add(q.peek());
            q.poll();
        }
 
        // Insert elements of q1 and q2 back
        // to q in alternate order.
        for (int i = 0; i < n / 2; i++) {
            q.add(q1.peek());
            q1.poll();
            q.add(q2.peek());
            q2.poll();
        }
    }
 
    // Driver code
    public static void main(String[] args)
    {
        // Creating an example queue with 10
        // elements.
        Queue q = new LinkedList();
        for (int i = 1; i <= 10; i++)
            q.add(i);
 
        interleave(q);
 
        // Printing queue elements
        int n = q.size();
        for (int i = 0; i < n; i++) {
            System.out.print(q.peek() + " ");
            q.poll();
        }
    }
}
 
// This code is contributed by jainlovely450

Python3

# Python3 program to interleave the first
# half of the queue with the second half
from queue import Queue
 
# Function to interleave the queue
def interLeaveQueue(q):
 
    # Initialize an empty stack of int type
    q1 = Queue()
    q2 = Queue()
    halfSize = int(q.qsize() / 2)
 
    # Insert first half in q1
    for i in range(halfSize):
        q1.put(q.queue[0])
        q.get()
 
    # Insert second half in q2
    for i in range(halfSize):
        q2.put(q.queue[0])
        q.get()
 
    # Insert elements of q1 and q2 back
    # to q in alternate order
    for i in range(halfSize):
        q.put(q1.queue[0])
        q1.get()
        q.put(q2.queue[0])
        q2.get()
 
# Driver Code
if __name__ == '__main__':
    q = Queue()
    q.put(1)
    q.put(2)
    q.put(3)
    q.put(4)
    q.put(5)
    q.put(6)
    q.put(7)
    q.put(8)
    q.put(9)
    q.put(10)
    interLeaveQueue(q)
    length = q.qsize()
    for i in range(length):
        print(q.queue[0], end=" ")
        q.get()
 
# This code is contributed by jainlovely450

输出：

1 6 2 7 3 8 4 9 5 10

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