如何从队列中移除特定元素
给定一个队列 q[] 和一个整数 K，任务是定义一个方法，从队列 q[] 中移除特定元素。如果元素 K、出现多次，则从队列 q[]中删除第一个。
示例:
输入: q[] = {10，20，30，40，50，60}，K = 30 输出: {10，20，40，50，60} 说明:去掉 30 后，队列变成{10，20，40，50，60}。
输入: q[] = {1，2，3，3}，K = 3 输出: {1，2，3} 解释:删除第一个出现的 3 后，队列变成{1，2，3}。
方法:想法是创建一个临时的队列ref【】并存储其中的所有元素，直到找到 K 。然后，从原队列 q[]、中移除 K ，将剩余元素插回队列 q[]。按照以下步骤解决问题:
- 初始化一个助手队列 ref 来临时存储队列q【】的元素。
- 将变量 s 初始化为队列q【】和 cnt 的大小为 0 ，以存储推入帮助者队列 的数字计数。
- 循环迭代直到队列 q[] 不为空，并且队列的前面不等于所需元素 K:
- 如果队列 q[] 为空，则元素 K 不在队列中 q[]、所以打印“元素未找到！!"并执行以下步骤:
- 否则，找到该元素，因此从队列中取出元素 q[] ，并执行以下步骤:
- 将变量 k 初始化为 s-cnt-1 ，以标记将从队列出列 q[] 和再次入队回到队列 q[]。
- 循环迭代直到 K 大于 0 ，执行以下步骤:
- 执行以上步骤后，打印队列 q[]的元素。
下面是上述方法的实现。
C++
// C++ program for the above approach.
#include <bits/stdc++.h>
using namespace std;
// Function to remove an element from
// the queue
void remove(int t, queue<int>& q)
{
// Helper queue to store the elements
// temporarily.
queue<int> ref;
int s = q.size();
int cnt = 0;
// Finding the value to be removed
while (q.front() != t and !q.empty()) {
ref.push(q.front());
q.pop();
cnt++;
}
// If element is not found
if (q.empty()) {
cout << "element not found!!" << endl;
while (!ref.empty()) {
// Pushing all the elements back into q
q.push(ref.front());
ref.pop();
}
}
// If element is found
else {
q.pop();
while (!ref.empty()) {
// Pushing all the elements back into q
q.push(ref.front());
ref.pop();
}
int k = s - cnt - 1;
while (k--) {
// Pushing elements from front of q to its back
int p = q.front();
q.pop();
q.push(p);
}
}
}
// Function to print all the elements
// of the queue.
void print(queue<int> qr)
{
while (!qr.empty()) {
cout << qr.front() << " ";
qr.pop();
}
cout << endl;
}
// Driver Code
int main()
{
queue<int> q;
// Pushing into the queue
q.push(10);
q.push(20);
q.push(30);
q.push(40);
q.push(50);
q.push(60);
print(q);
// Removing 39 from the queue
remove(39, q);
print(q);
// Removing 30 from the queue
remove(30, q);
print(q);
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java program for the above approach.
import java.util.*;
class GFG{
// Function to remove an element from
// the queue
static Queue<Integer> q;
static void remove(int t)
{
// Helper queue to store the elements
// temporarily.
Queue<Integer> ref = new LinkedList<>();
int s = q.size();
int cnt = 0;
// Finding the value to be removed
while (!q.isEmpty() && q.peek() != t) {
ref.add(q.peek());
q.remove();
cnt++;
}
// If element is not found
if (q.isEmpty()) {
System.out.print("element not found!!" +"\n");
while (!ref.isEmpty()) {
// Pushing all the elements back into q
q.add(ref.peek());
ref.remove();
}
}
// If element is found
else {
q.remove();
while (!ref.isEmpty()) {
// Pushing all the elements back into q
q.add(ref.peek());
ref.remove();
}
int k = s - cnt - 1;
while (k-- >0) {
// Pushing elements from front of q to its back
int p = q.peek();
q.remove();
q.add(p);
}
}
}
// Function to print all the elements
// of the queue.
static void print()
{
Queue<Integer> qr = new LinkedList<>(q);
while (!qr.isEmpty()) {
System.out.print(qr.peek()+ " ");
qr.remove();
}
System.out.println();
}
// Driver Code
public static void main(String[] args)
{
q = new LinkedList<>();
// Pushing into the queue
q.add(10);
q.add(20);
q.add(30);
q.add(40);
q.add(50);
q.add(60);
print();
// Removing 39 from the queue
remove(39);
print();
// Removing 30 from the queue
remove(30);
print();
}
}
// This code is contributed by 29AjayKumar
C
// C# program for the above approach.
using System;
using System.Collections;
public class GFG{
// Function to remove an element from
// the queue
static Queue q = new Queue();
static void remove_(int t)
{
// Helper queue to store the elements
// temporarily.
Queue reff = new Queue();
int s = q.Count;
int cnt = 0;
// Finding the value to be removed
while ((int)q.Count != 0 && (int)q.Peek() != t) {
reff.Enqueue(q.Peek());
q.Dequeue();
cnt++;
}
// If element is not found
if (q.Count == 0) {
Console.WriteLine("element not found!!");
while (reff.Count != 0) {
// Pushing all the elements back into q
q.Enqueue(reff.Peek());
reff.Dequeue();
}
}
// If element is found
else {
q.Dequeue();
while (reff.Count != 0) {
// Pushing all the elements back into q
q.Enqueue(reff.Peek());
reff.Dequeue();
}
int k = s - cnt - 1;
while (k-- >0) {
// Pushing elements from front of q to its back
int p = (int)q.Peek();
q.Dequeue();
q.Enqueue(p);
}
}
}
// Function to print all the elements
// of the queue.
static void print()
{
Queue qr = (Queue)q.Clone();
while (qr.Count != 0) {
Console.Write(qr.Peek()+ " ");
qr.Dequeue();
}
Console.WriteLine();
}
// Driver Code
static public void Main (){
// Pushing into the queue
q.Enqueue(10);
q.Enqueue(20);
q.Enqueue(30);
q.Enqueue(40);
q.Enqueue(50);
q.Enqueue(60);
print();
// Removing 39 from the queue
remove_(39);
print();
// Removing 30 from the queue
remove_(30);
print();
}
}
// This code is contributed by Dharanendra L V.
Output
10 20 30 40 50 60
element not found!!
10 20 30 40 50 60
10 20 40 50 60
时间复杂度:O(N) T5辅助空间:** O(N)
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