等于其频率的数组中的最大元素

给定大小为N的整数arr []数组，任务是在数组中查找其frequecny等于其值的最大元素

例子：

Input: arr[] = {3, 2, 2, 3, 4, 3}
Output: 3
Frequency of element 2 is 2
Frequency of element 3 is 3
Frequency of element 4 is 1
2 and 3 are elements which have same frequency as it’s value and 3 is the maximum.

Input: arr[] = {1, 2, 3, 4, 5, 6}
Output: 1

方法：使用映射存储数组每个元素的频率，最后找出频率等于其值的那些元素的最大值。

下面是上述方法的实现：

CPP

// C++ program to find the maximum element 
// whose frequency equals to it’s value
  
#include 
using namespace std;
  
// Function to find the maximum element 
// whose frequency equals to it’s value
int find_maxm(int arr[], int n)
{
    // Hash map for counting frquency
    map mpp;
  
    for (int i = 0; i < n; i++) {
        // Counting freq of each element
        mpp[arr[i]] += 1;
    }
  
    int ans = 0;
    for (auto x : mpp)
    {
        int value = x.first;
        int freq = x.second;
          
        // Check if value equls to frequency
        // and it is the maximum element or not
        if (value == freq) {
            ans = max(ans, value);
        }
    }
  
    return ans;
}
  
// Driver code
int main()
{
    int arr[] = { 3, 2, 2, 3, 4, 3 };
      
    // Size of array
    int n = sizeof(arr) / sizeof(arr[0]);
      
    // Function call
    cout << find_maxm(arr, n);
  
    return 0;
}

Java

// Java program to find the maximum element 
// whose frequency equals to it’s value
import java.util.*;
  
class GFG{
   
// Function to find the maximum element 
// whose frequency equals to it’s value
static int find_maxm(int arr[], int n)
{
    // Hash map for counting frquency
    HashMap mp = new HashMap();
   
    for (int i = 0; i < n; i++) {
          
        // Counting freq of each element
        if(mp.containsKey(arr[i])){
            mp.put(arr[i], mp.get(arr[i])+1);
        }else{
            mp.put(arr[i], 1);
    }
    }
   
    int ans = 0;
    for (Map.Entry x : mp.entrySet())
    {
        int value = x.getKey();
        int freq = x.getValue();
           
        // Check if value equls to frequency
        // and it is the maximum element or not
        if (value == freq) {
            ans = Math.max(ans, value);
        }
    }
   
    return ans;
}
   
// Driver code
public static void main(String[] args)
{
    int arr[] = { 3, 2, 2, 3, 4, 3 };
       
    // Size of array
    int n = arr.length;
       
    // Function call
    System.out.print(find_maxm(arr, n));
   
}
}
  
// This code is contributed by 29AjayKumar

Python3

# Python3 program to find the maximum element 
# whose frequency equals to it’s value 
  
# Function to find the maximum element 
# whose frequency equals to it’s value 
def find_maxm(arr, n) :
  
    # Hash map for counting frquency 
    mpp = {}
  
    for i in range(0,n):
        # Counting freq of each element 
        if(arr[i] in mpp):
            mpp.update( {arr[i] : mpp[arr[i]] + 1} )
        else:
            mpp[arr[i]] = 1
  
    ans = 0
    for value,freq in mpp.items():
        # Check if value equls to frequency 
        # and it is the maximum element or not 
        if (value == freq):
            ans = max(ans, value)
  
    return ans
  
# Driver code 
arr = [ 3, 2, 2, 3, 4, 3 ]
      
# Size of array 
n = len(arr)
  
# Function call 
print(find_maxm(arr, n))
  
# This code is contributed by Sanjit_Prasad

C#

// C# program to find the maximum element 
// whose frequency equals to it’s value
using System;
using System.Collections.Generic;
  
class GFG{
    
// Function to find the maximum element 
// whose frequency equals to it’s value
static int find_maxm(int []arr, int n)
{
    // Hash map for counting frquency
    Dictionary mp = new Dictionary();
    
    for (int i = 0; i < n; i++) {
           
        // Counting freq of each element
        if(mp.ContainsKey(arr[i])){
            mp[arr[i]] = mp[arr[i]]+1;
        }else{
            mp.Add(arr[i], 1);
    }
    }
    
    int ans = 0;
    foreach (KeyValuePair x in mp)
    {
        int value = x.Key;
        int freq = x.Value;
            
        // Check if value equls to frequency
        // and it is the maximum element or not
        if (value == freq) {
            ans = Math.Max(ans, value);
        }
    }
    
    return ans;
}
    
// Driver code
public static void Main(String[] args)
{
    int []arr = { 3, 2, 2, 3, 4, 3 };
        
    // Size of array
    int n = arr.Length;
        
    // Function call
    Console.Write(find_maxm(arr, n));
}
}
  
// This code is contributed by Rajput-Ji

输出：

3