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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3.  
  4. void Merge(int arr[],int start,int mid, int end)
  5. {
  6.  
  7.     int n1=mid-start+1; /// size of left array
  8.     int n2=end-mid; /// size of right array
  9.     int L[n1],R[n2];
  10.  
  11.  
  12.  
  13.     for(int i=0; i<n1; i++)
  14.     {
  15.  
  16.         L[i]=arr[start+i];
  17.     }
  18.  
  19.     for(int i=0; i<n2; i++)
  20.     {
  21.  
  22.         R[i]=arr[mid+1+i];
  23.     }
  24.  
  25.     int i=0,j=0,k=start;
  26.     while(i<n1 && j<n2)
  27.     {
  28.         if(L[i]<=R[j])
  29.         {
  30.             arr[k]=L[i];
  31.             i++;
  32.             k++;
  33.         }
  34.         else
  35.         {
  36.             arr[k]=R[j];
  37.             j++;
  38.             k++;
  39.         }
  40.     }
  41.     while(j<n2)
  42.     {
  43.         arr[k]=R[j];
  44.         j++;
  45.         k++;
  46.     }
  47.     while(i<n1)
  48.     {
  49.         arr[k]=L[i];
  50.         i++;
  51.         k++;
  52.     }
  53.  
  54.  
  55. }
  56.  
  57. void mergeSort(int arr[], int start, int end)
  58. {
  59.  
  60.  
  61.     if (start<end)
  62.     {
  63.         int mid=(start+end)/2;
  64.         mergeSort(arr,start,mid);
  65.         mergeSort (arr, mid+1,end);
  66.         Merge(arr,start,mid,end);
  67.     }
  68. }
  69.  
  70. int main()
  71. {
  72.  
  73.     int arr[]= {21,3,54,-45,78,2,-1};
  74.     int n= sizeof(arr)/sizeof(arr[0]);
  75.  
  76.     mergeSort(arr,0,n-1);
  77.  
  78.     cout<<"after sorting in descendig order: ";
  79.     for(int i=n-1; i>=0; i--)
  80.     {
  81.         cout<<arr[i]<<" ";
  82.     }
  83.     cout<<endl;
  84.     cout<<"after sorting in ascending order: ";
  85.     for(int i=0; i<n; i++)
  86.     {
  87.         cout<<arr[i]<<" ";
  88.     }
  89.     return 0;
  90. }
  91.  
Success #stdin #stdout 0.01s 5316KB
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stdin
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Standard input is empty
stdout
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after sorting in descendig order: 78 54 21 3 2 -1 -45 
after sorting in ascending order: -45 -1 2 3 21 54 78
https://ideone.com/j2jXCj
language:
C++ (gcc 8.3)
created:
16 hours ago
visibility:
public

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