删除给定元素后找出k个最大的数

给定一个整数数组，找出删除给定元素后的 k 个最大数。在重复元素的情况下，对于包含要删除的元素的数组中存在的元素的每个实例，删除一个实例。
假设删除n个元素后至少会留下k个元素。
例子：
输入：数组[] = { 5, 12, 33, 4, 56, 12, 20 }, del[] = { 12, 56, 5 }, k = 3
输出：33 20 12
说明：删除后会留下 { 33, 4, 12, 20 } 。从中打印前 3 个最高元素。

方法 ：

• 将哈希映射中所有要从数组中删除的数字插入，以便我们可以在 O(1) 时间内检查数组中的元素是否也存在于 Delete-array 中。
• 遍历数组。检查该元素是否存在于哈希映射中。
• 如果存在，将其从哈希映射中删除。
• 否则，将其插入最大堆。
• 插入除要删除的元素之外的所有元素后，从Max堆中弹出k个元素。

C++

#include "iostream"
#include "queue"
#include "unordered_map"
using namespace std;
 
// Find k maximum element from arr[0..m-1] after deleting
// elements from del[0..n-1]
void findElementsAfterDel(int arr[], int m, int del[],
                                        int n, int k)
{
    // Hash Map of the numbers to be deleted
    unordered_map mp;
    for (int i = 0; i < n; ++i) {
 
        // Increment the count of del[i]
        mp[del[i]]++;
    }
 
    // Initializing the largestElement
    priority_queue heap;
 
    for (int i = 0; i < m; ++i) {
 
        // Search if the element is present
        if (mp.find(arr[i]) != mp.end()) {
 
            // Decrement its frequency
            mp[arr[i]]--;
 
            // If the frequency becomes 0,
            // erase it from the map
            if (mp[arr[i]] == 0)
                mp.erase(arr[i]);
        }
 
        // Else compare it largestElement
        else
            heap.push(arr[i]);
    }
 
    // Print top k elements in the heap
    for (int i = 0; i < k; ++i) {
        cout << heap.top() << " ";
 
        // Pop the top element
        heap.pop();
    }
}
 
int main()
{
    int array[] = { 5, 12, 33, 4, 56, 12, 20 };
    int m = sizeof(array) / sizeof(array[0]);
 
    int del[] = { 12, 56, 5 };
    int n = sizeof(del) / sizeof(del[0]);
 
    int k = 3;
 
    findElementsAfterDel(array, m, del, n, k);
    return 0;
}

Java

import java.io.*;
import java.util.*;
 
class GFG
{
 
  // Find k maximum element from arr[0..m-1] after deleting
  // elements from del[0..n-1]
  static void findElementsAfterDel(int arr[], int m,
                                   int del[], int n, int k)
  {
 
    // Hash Map of the numbers to be deleted
    Map mp = new HashMap();
    for (int i = 0; i < n; ++i)
    {
 
      // Increment the count of del[i]
      if(mp.containsKey(del[i]))
      {         
        mp.put(del[i], mp.get(del[i]) + 1);
      }
      else
      {
        mp.put(del[i], 1);
      }
    }
 
    // Initializing the largestElement
    PriorityQueue heap =
      new PriorityQueue(
      Collections.reverseOrder());
    for (int i = 0; i < m; ++i)
    {
 
      // Search if the element is present
      if(mp.containsKey(arr[i]))
      {
 
        // Decrement its frequency
        mp.put(arr[i], mp.get(arr[i]) - 1);
 
        // If the frequency becomes 0,
        // erase it from the map
        if(mp.get(arr[i]) == 0)
        {
          mp.remove(arr[i]);
        }
      }
 
      // Else compare it largestElement
      else
      {
        heap.add(arr[i]);
      }
    }
 
    // Print top k elements in the heap
    for(int i = 0; i < k; ++i)
    {
      // Pop the top element
      System.out.print(heap.poll() + " ");
    }
  }
 
  // Driver code
  public static void main (String[] args)
  {
    int array[] = { 5, 12, 33, 4, 56, 12, 20 };
    int m = array.length;
    int del[] = { 12, 56, 5 };
    int n = del.length;
    int k = 3;
    findElementsAfterDel(array, m, del, n, k);
  }
}
 
// This code is contributed by rag2127

Python3

# Python3 program to find the k maximum
# number from the array after n deletions
import math as mt
 
# Find k maximum element from arr[0..m-1]
# after deleting elements from del[0..n-1]
def findElementsAfterDel(arr, m, dell, n, k):
 
    # Hash Map of the numbers to be deleted
    mp = dict()
    for i in range(n):
         
        # Increment the count of del[i]
        if dell[i] in mp.keys():
            mp[dell[i]] += 1
        else:
            mp[dell[i]] = 1
             
    heap = list()
     
    for i in range(m):
         
        # Search if the element is present
        if (arr[i] in mp.keys()):
             
            # Decrement its frequency
            mp[arr[i]] -= 1
 
            # If the frequency becomes 0,
            # erase it from the map
            if (mp[arr[i]] == 0):
                mp.pop(arr[i])
 
        # Else push it
        else:
            heap.append(arr[i])
     
    heap.sort()
    heap = heap[::-1]
    return heap[:k]
 
# Driver code
array = [5, 12, 33, 4, 56, 12, 20]
m = len(array)
 
dell = [12, 4, 56, 5 ]
n = len(dell)
k = 3
print(*findElementsAfterDel(array, m, dell, n, k))
 
# This code is contributed by
# mohit kumar 29

C#

using System;
using System.Collections.Generic;
 
class GFG
{
 
  // Find k maximum element from arr[0..m-1] after deleting
  // elements from del[0..n-1]
  static void findElementsAfterDel(int[] arr, int m,
                                   int[] del, int n, int k)
  {
 
    // Hash Map of the numbers to be deleted
    Dictionary mp = new Dictionary();
    for (int i = 0; i < n; ++i)
    {
 
      // Increment the count of del[i]
      if(mp.ContainsKey(del[i]))
      {
        mp[del[i]]++;
      }
      else
      {
        mp.Add(del[i], 1);
      }
    }
 
    // Initializing the largestElement
    List heap = new List();
    for (int i = 0; i < m; ++i)
    {
 
      // Search if the element is present
      if(mp.ContainsKey(arr[i]))
      {
 
        // Decrement its frequency
        mp[arr[i]]--;
 
        // If the frequency becomes 0,
        // erase it from the map
        if(mp[arr[i]] == 0)
        {
          mp.Remove(arr[i]);
        }
      }
 
      // Else compare it largestElement
      else
      {
        heap.Add(arr[i]);
      }
    }
    heap.Sort();
    heap.Reverse();
 
    // Print top k elements in the heap
    for(int i = 0; i < k; ++i)
    {
      Console.Write(heap[i] + " ");
    }       
  }
 
  // Driver code
  static public void Main ()
  {
    int[] array = { 5, 12, 33, 4, 56, 12, 20 };
    int m = array.Length;
    int[] del = { 12, 56, 5 };
    int n = del.Length;
    int k = 3;
    findElementsAfterDel(array, m, del, n, k);
  }
}
 
// This code is contributed by avanitrachhadiya2155

Javascript

 
// Find k maximum element from arr[0..m-1] after deleting
// elements from del[0..n-1]
function findElementsAfterDel(arr,m,del,n,k)
{
    // Hash Map of the numbers to be deleted
    let mp = new Map();
    for (let i = 0; i < n; ++i)
    {
  
      // Increment the count of del[i]
      if(mp.has(del[i]))
      {        
        mp.set(del[i], mp.get(del[i]) + 1);
      }
      else
      {
        mp.set(del[i], 1);
      }
    }
  
    // Initializing the largestElement
    let heap =[];
    for (let i = 0; i < m; ++i)
    {
  
      // Search if the element is present
      if(mp.has(arr[i]))
      {
  
        // Decrement its frequency
        mp.set(arr[i], mp.get(arr[i]) - 1);
  
        // If the frequency becomes 0,
        // erase it from the map
        if(mp.get(arr[i]) == 0)
        {
          mp.delete(arr[i]);
        }
      }
  
      // Else compare it largestElement
      else
      {
        heap.push(arr[i]);
      }
    }
      
    heap.sort(function(a,b){return b-a;});
     
    // Print top k elements in the heap
    for(let i = 0; i < k; ++i)
    {
      // Pop the top element
      document.write(heap[i] + " ");
    }
}
 
// Driver code
let array=[ 5, 12, 33, 4, 56, 12, 20 ];
let m = array.length;
let del=[12, 56, 5];
let n = del.length;
let k = 3;
findElementsAfterDel(array, m, del, n, k);
     
 
// This code is contributed by unknown2108
 

输出：

33 20 12