To find the element with odd number of occurences, we can simply store frequenct of every element. To do so, we can use a map to track the frequencies.

Traverse the entire array and increment frequency of every element in the map.
Once the array is traversed, look in the map for frequency of every key.
Return the key with odd value.

Code

#include <bits/stdc++.h>
using namespace std;

class Solution {
public:
    // Function to find element with odd occurence
    int findOddOccurrence(vector<int>& nums) {
        // Create a map to store frequency
        unordered_map<int, int> freq;

        // Count frequency of each number
        for (int num : nums) {
            freq[num]++;
        }

        // Return the element with odd frequency
        for (auto it : freq) {
            if (it.second % 2 == 1) {
                return it.first;
            }
        }

        // Return -1 if no odd occurrence found
        return -1;
    }
};

int main() {
    vector<int> nums = {2, 3, 2, 3, 5, 5, 7};
    Solution obj;
    cout << obj.findOddOccurrence(nums) << endl;
    return 0;
}
import java.util.*;

class Solution {
    // Function to find element with odd occurence
    public int findOddOccurrence(int[] nums) {
        // Create a map to store frequency
        HashMap<Integer, Integer> freq = new HashMap<>();

        // Count frequency of each number
        for (int num : nums) {
            freq.put(num, fre