def countingSort(arr):
    # Write your code here
    count = [0]*100
    for n in arr: 
        count[n] += 1
    
    return count

vector<int> countingSort(vector<int> arr) {
    vector<int> count(100); // arrays connot be returned so make sure to use vectors
    for (int i = 0; i < arr.size(); i++){ 
    // for vectors use size() method the length() method works for strings only
        count[arr[i]]++;        
    }
    return count;
}

vector<int> countingSort(vector<int> arr) {
    vector<int> count(100);  
    for (int i = 0; i < arr.size(); i++){ 
        count[arr[i]]++;        
    }
    return count;
}

💬 If you're new to leetcode don't bother trying to solve it I will share more feasible questions for beginners.

class Solution:
    def sortEvenOdd(self, nums: List[int]) -> List[int]:
        n = len(nums)
        
        even_indexes = [nums[i] for i in range(0, n, 2)]
        # range(start, end, step)
        odd_indexes = [nums[i] for i in range(1, n, 2)]

        even_indexes.sort()
        odd_indexes.sort(reverse=True)

        even_ptr = odd_ptr = 0
        res = []
        for i in range(n):
            if i % 2 == 0:
                res.append(even_indexes[even_ptr])
                even_ptr += 1
            else:
                res.append(odd_indexes[odd_ptr])
                odd_ptr += 1
        
        return res

class Solution:
    def sortEvenOdd(self, nums: List[int]) -> List[int]:
        nums[::2] = sorted(nums[::2])
        nums[1::2] = sorted(nums[1::2], reverse=True)
        return nums

// #include <bits/std++.h> 
// using namespace std;
// If you are running it locally make sure to include the above in your code

class Solution {
public:
    vector<int> sortEvenOdd(vector<int>& nums) {
        int n = nums.size();
        
        vector<int> even_indexes;
        vector<int> odd_indexes;
        
        for (int i = 0; i < n; i += 2) {
            even_indexes.push_back(nums[i]);
        }
        
        for (int i = 1; i < n; i += 2) {
            odd_indexes.push_back(nums[i]);
        }

        sort(even_indexes.begin(), even_indexes.end());
        sort(odd_indexes.rbegin(), odd_indexes.rend());

        int even_ptr = 0, odd_ptr = 0;
        vector<int> res(n);
        
        for (int i = 0; i < n; ++i) {
            if (i % 2 == 0) {
                res[i] = even_indexes[even_ptr++];
            } else {
                res[i] = odd_indexes[odd_ptr++];
            }
        }
        
        return res;
    }
};

🎉 Quiz Time! 🚀