矩阵中所有偶数频率元素的总和

给定包含重复元素的 NxM 整数矩阵。任务是找到给定矩阵中所有偶数出现的元素的总和。那是矩阵中频率为偶数的所有此类元素的总和。
例子：

Input : mat[] = {{1, 1, 2},
                {2, 3, 3},
                {4, 5, 3}}
Output : 18
The even occurring elements are 1, 2 and their number
of occurrences are 2, 2 respectively. Therefore,
sum = 1+1+2+2 = 6.

Input : mat[] = {{10, 20},
                 {40, 40}}
Output : 80

方法：

• 遍历矩阵并使用map来存储矩阵元素的频率，使得map的key是矩阵元素，value是它在矩阵中的频率。
• 然后，遍历地图以查找元素的频率并检查它是否为偶数，然后将此元素的频率乘以求和。

下面是上述方法的实现：

C++

// C++ program to find sum of all even
// frequency elements in a Matrix
 
#include 
using namespace std;
 
#define N 3 // Rows
#define M 3 // Columns
 
// Function to find sum of all even
// frequency elements in a Matrix
int sumOddOccurring(int arr[N][M])
{
 
    // Store frequency of elements
    // in matrix
    unordered_map mp;
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < M; j++) {
            mp[arr[i][j]]++;
        }
    }
 
    // Sum even frequency elements
    int sum = 0;
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        if (itr->second % 2 == 0) {
            int x = itr->second;
            sum += (itr->first) * (itr->second);
        }
    }
 
    return sum;
}
 
// Driver Code
int main()
{
 
    int mat[N][M] = { { 1, 2, 3 },
                      { 1, 3, 2 },
                      { 1, 5, 6 } };
 
    cout << sumOddOccurring(mat) << endl;
 
    return 0;
}

Java

// Java program to find sum of all even
// frequency elements in a Matrix
import java.util.*;
 
class GFG
{
 
static final int N = 3; // Rows
static final int M = 3; // Columns
 
// Function to find sum of all even
// frequency elements in a Matrix
static int sumOddOccurring(int arr[][])
{
 
    // Store frequency of elements
    // in matrix
    Map mp = new HashMap();
    for (int i = 0; i < N; i++)
    {
        for (int j = 0; j < M; j++)
        {
            if(mp.get(arr[i][j]) == null)
                mp.put(arr[i][j], 1);
            else
                mp.put(arr[i][j],
                      (mp.get(arr[i][j]) + 1));
        }
    }
 
    // Sum even frequency elements
    int sum = 0;
    Set< Map.Entry > st = mp.entrySet();
 
    for (Map.Entry< Integer, Integer> me:st)
    {
        if (me.getValue() % 2 == 0)
        {
            int x = me.getValue();
            sum += (me.getKey()) * (me.getValue());
        }
    }
    return sum;
}
 
// Driver Code
public static void main(String args[])
{
    int mat[][] = {{ 1, 2, 3 },
                   { 1, 3, 2 },
                   { 1, 5, 6 }};
 
    System.out.print(sumOddOccurring(mat));
}
}
 
// This code is contributed by Arnab Kundu

Python3

# Python3 program to find sum of all even
# frequency elements in a Matrix
import sys
 
N = 3 # Rows
M = 3 # Columns
 
# Function to find sum of all even
# frequency elements in a Matrix
def sumOddOccuring(arr):
 
    # Store frequencies of elements
    # in matrix
    mp = dict()
    for i in range(N):
        for j in range(M):
            if arr[i][j] in mp:
                mp[arr[i][j]] += 1
            else:
                mp[arr[i][j]] = 1
 
    # Sum of even frequency elements
    s = 0
    for i in mp:
        if mp[i] % 2 == 0:
            x = mp[i]
            s += i * mp[i]
 
    return s
 
# Driver code
if __name__ == "__main__":
    mat = [[1, 2, 3],
           [1, 3, 2],
           [1, 5, 6]]
 
    print(sumOddOccuring(mat))
 
# This code is contributed by
# sanjeev2552

C#

// C# program to find sum of all even
// frequency elements in a Matrix
using System;
using System.Collections.Generic;
 
class Sol
{
 
static readonly int N = 3; // Rows
static readonly int M = 3; // Columns
 
// Function to find sum of all even
// frequency elements in a Matrix
static int sumOddOccurring(int [,]arr)
{
 
    // Store frequency of elements
    // in matrix
    Dictionary mp = new Dictionary();
    for (int i = 0; i < N; i++)
    {
        for (int j = 0; j < M; j++)
        {
            if(!mp.ContainsKey(arr[i, j]))
                mp.Add(arr[i, j], 1);
            else{
                var val = mp[arr[i, j]];
                mp.Remove(arr[i, j]);
                mp.Add(arr[i, j], val + 1);
            }
        }
    }
 
    // Sum even frequency elements
    int sum = 0;
    foreach(KeyValuePair entry in mp)
    {
        if(entry.Value % 2 == 0){
            sum += entry.Key * entry.Value;
        }
    }
 
    return sum;
}
 
// Driver Code
public static void Main(String []args)
{
 
    int [,]mat = { { 1, 2, 3 },
                    { 1, 3, 2 },
                    { 1, 5, 6 } };
 
    Console.Write( sumOddOccurring(mat) );
 
}
}
 
/* This code contributed by PrinciRaj1992 */

Javascript

 
// JavaScript program to find sum of all even
// frequency elements in a Matrix
 
var N = 3; // Rows
var M = 3; // Columns
 
// Function to find sum of all even
// frequency elements in a Matrix
function sumOddOccurring(arr)
{
 
    // Store frequency of elements
    // in matrix
    var mp = new Map();
    for (var i = 0; i < N; i++)
    {
        for (var j = 0; j < M; j++)
        {
            if(!mp.has(arr[i][j]))
                mp.set(arr[i][j], 1);
            else{
                var val = mp.get(arr[i][j]);
                mp.delete(arr[i][j]);
                mp.set(arr[i][j], val + 1);
            }
        }
    }
 
    // Sum even frequency elements
    var sum = 0;
    mp.forEach((value, key) => {
        if(value % 2 == 0){
            sum += key * value;
        }
    });
 
    return sum;
}
 
// Driver Code
var mat = [[1, 2, 3 ],
                [1, 3, 2 ],
                [1, 5, 6 ]];
document.write( sumOddOccurring(mat) );
 
 
 

输出：

10

时间复杂度： O(N x M)
辅助空间： O(N x M)

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