STL Priority Queue 是堆数据结构的实现。默认情况下,它是最大堆,并且可以轻松用于原始数据类型。在本文中可以找到它的一些重要应用。
优先队列可以通过两种方式初始化,一种是将所有元素一一推送,另一种是使用它们的构造函数进行初始化。在本文中,我们将讨论这两种方法并检查它们的时间复杂度。
方法一:最简单的方法就是遍历给定的数组,将每个元素一一压入优先级队列。在这个方法中,优先队列中的push方法需要O(log N)的时间。其中N是数组中的元素数。
下面是上述方法的实现:
C++
// C++ program to initialize the
// priority queue
#include
using namespace std;
// Driver Code
int main()
{
int arr[] = { 15, 25, 6, 54, 45, 26, 12 };
int N = sizeof(arr) / sizeof(arr[0]);
// Initialize priority_queue
priority_queue pq;
// Traverse the array arr[]
for (int i = 0; i < N; i++) {
// Push the element arr[i]
pq.push(arr[i]);
}
cout << "The elements in priority"
<< " Queue are: ";
// Traverse until pq is non-empty
while (!pq.empty()) {
// Print the element in pq
cout << pq.top() << " ";
// Pop the top element
pq.pop();
}
return 0;
}
Java
// Java program to initialize the
// priority queue
import java.util.*;
public class GFG
{
public static void main(String[] args)
{
int[] arr = { 15, 25, 6, 54, 45, 26, 12 };
int N = arr.length;
// Initialize priority_queue
Vector pq = new Vector();
// Traverse the array arr[]
for (int i = 0; i < N; i++)
{
// Push the element arr[i]
pq.add(arr[i]);
}
Collections.sort(pq);
Collections.reverse(pq);
System.out.print("The elements in priority" + " Queue are: ");
// Traverse until pq is non-empty
while (pq.size() > 0)
{
// Print the element in pq
System.out.print(pq.get(0) + " ");
// Pop the top element
pq.remove(0);
}
}
}
// This code is contributed by divyesh072019.
Python3
# Python3 program to initialize the
# priority queue
# Driver Code
if __name__ == '__main__':
arr = [15, 25, 6, 54, 45, 26, 12]
N = len(arr)
# Initialize priority_queue
pq = []
# Traverse the array arr[]
for i in range(N):
# Push the element arr[i]
pq.append(arr[i])
print("The elements in priority Queue are: ", end = "")
pq = sorted(pq)
# Traverse until pq is non-empty
while (len(pq) > 0):
# Print the element in pq
print(pq[-1], end = " ")
# Pop the top element
del pq[-1]
# This code is contributed by mohit kumar 29.
C#
// C# program to initialize the
// priority queue
using System;
using System.Collections.Generic;
class GfG
{
public static void Main()
{
int[] arr = { 15, 25, 6, 54, 45, 26, 12 };
int N = arr.Length;
// Initialize priority_queue
List pq = new List();
// Traverse the array arr[]
for (int i = 0; i < N; i++) {
// Push the element arr[i]
pq.Add(arr[i]);
}
pq.Sort();
pq.Reverse();
Console.Write("The elements in priority" + " Queue are: ");
// Traverse until pq is non-empty
while (pq.Count > 0) {
// Print the element in pq
Console.Write(pq[0] + " ");
// Pop the top element
pq.RemoveAt(0);
}
}
}
// This code is contributed by divyeshrabadiya07.
Javascript
C++
// C++ program to initialize the
// priority queue
#include
#include
using namespace std;
// Driver Code
int main()
{
int arr[] = { 15, 25, 6, 54, 45, 26, 12 };
int N = sizeof(arr) / sizeof(arr[0]);
// By this type of initialization
// the priority_queue is using
// build heap to make the max heap
cout << "The elements in priority"
<< " Queue are: ";
// Initialize priority_queue
priority_queue pq(arr, arr + N);
// Iterate until pq is non empty
while (!pq.empty()) {
// Print the element
cout << pq.top() << " ";
pq.pop();
}
return 0;
}
Python3
# Python3 program to initialize the
# priority queue
# Driver Code
if __name__=='__main__':
arr = [ 15, 25, 6, 54, 45, 26, 12 ]
N = len(arr)
# By this type of initialization
# the priority_queue is using
# build heap to make the max heap
print("The elements in priority Queue are: ", end = '')
# Initialize priority_queue
pq = arr
pq.sort()
# Iterate until pq is non empty
while (len(pq) != 0):
# Print the element
print(pq[-1], end = ' ')
pq.pop()
# This code is contributed by rutvik_56.
The elements in priority Queue are: 54 45 26 25 15 12 6
时间复杂度: O(N*log N)
辅助空间: O(N)
方法二:在该方法中,在初始化优先级队列时,将所有数组元素复制到优先级队列中(这种复制将使用priority_queue的复制构造函数进行)。在此方法中, priority_queue将在内部使用构建堆方法。所以构建堆方法需要O(N)时间。
句法:
priority_queue
数组的语法:
priority_queue
where arr is the array and N is the size of the array.
向量的语法:
priority_queue
where v is the vector.
下面是上述方法的实现:
C++
// C++ program to initialize the
// priority queue
#include
#include
using namespace std;
// Driver Code
int main()
{
int arr[] = { 15, 25, 6, 54, 45, 26, 12 };
int N = sizeof(arr) / sizeof(arr[0]);
// By this type of initialization
// the priority_queue is using
// build heap to make the max heap
cout << "The elements in priority"
<< " Queue are: ";
// Initialize priority_queue
priority_queue pq(arr, arr + N);
// Iterate until pq is non empty
while (!pq.empty()) {
// Print the element
cout << pq.top() << " ";
pq.pop();
}
return 0;
}
蟒蛇3
# Python3 program to initialize the
# priority queue
# Driver Code
if __name__=='__main__':
arr = [ 15, 25, 6, 54, 45, 26, 12 ]
N = len(arr)
# By this type of initialization
# the priority_queue is using
# build heap to make the max heap
print("The elements in priority Queue are: ", end = '')
# Initialize priority_queue
pq = arr
pq.sort()
# Iterate until pq is non empty
while (len(pq) != 0):
# Print the element
print(pq[-1], end = ' ')
pq.pop()
# This code is contributed by rutvik_56.
The elements in priority Queue are: 54 45 26 25 15 12 6
时间复杂度: O(N)
辅助空间: O(N)
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