Sort array using merge sort

I am using merge sort for descending my array. What is the reason that my first element changed his value? My half code works. But with my first and last elements something went wrong.

#include <iostream>    void Merge(int a[], int low, int high, int mid)  {      int i = low, j = mid + 1, k = 0;      int temp[high - low + 1];        while (i <= mid && j <= high) {          if (a[i] > a[j])              temp[k++] = a[i++];            else              temp[k++] = a[j++];      }        while (i <= mid) {          temp[k++] = a[i++];      }        while (j <= high) {          temp[k++] = a[j++];      }      for (i = low; i <= high; i++) {          a[i] = temp[i - low];      }      return;  }    void MergeSort(int a[], int low, int high)  {      int mid;      if (low < high) {          mid = (low + high) / 2;          MergeSort(a, low, mid);          MergeSort(a, mid + 1, high);            Merge(a, low, high, mid);      }        return;  }    void output(int* a, int n)  {      for (int i = 0; i < n; i++) {          std::cout << a[i] << "\t";      }  }    int main()  {      int n;      std::cin >> n;      int a[n];      for (int i = 0; i < n; i++) {          std::cin >> a[i];      }      MergeSort(a, 0, n);      output(a, n);  }  

The output must be this.

input 10

1 2 3 4 5 6 7 8 9 10  

output

10 9 8 7 6 5 4 3 2 1  

But I'm getting this output

4197055 10  9   8   7   6   5   4   3   2   

I'm a beginner in a c++. So I will be happy if you can help me to do my first steps here.

https://stackoverflow.com/questions/65942286/sort-array-using-merge-sort January 29, 2021 at 01:31AM