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MergeSort.cpp
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MergeSort.cpp
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#include<iostream>
#include<vector>
#define MAX 100000
using namespace std;
//You are given two sorted arrays A and B. You want to merge these arrays and return a sorted vector will elements from both arrays.
void merge(vector<int> &a, vector<int> &b, vector<int> &toreturn)
{
int apointer = 0, bpointer = 0; //point to the first element in the vectors
//That hasn't been taken yet
while(apointer<a.size() && bpointer<b.size())
{
if(a[apointer]<=b[bpointer]){
toreturn.push_back(a[apointer++]);
}
else{ //b[bpointer] < a[apointer]
// inv += (a.size() - apointer);
toreturn.push_back(b[bpointer++]);
}
}
while(apointer<a.size()) toreturn.push_back(a[apointer++]);
while(bpointer<b.size()) toreturn.push_back(b[bpointer++]);
}
void ms(int arr[], int s, int e){
// cout<<s<<" "<<e<<endl;
if(s==e){// there is only one or no element
return;
}
int mid = (s+e)/2;
ms(arr, s, mid);
ms(arr, mid+1, e);
// Now arr[] has two sorted parts inside it.
// We have to take them out, merge the two parts and
// then resassign the values to arr[]
vector<int> a,b;
for(int i=s; i<=mid; i++) a.push_back(arr[i]);
for(int i=mid+1; i<=e; i++) b.push_back(arr[i]);
vector<int> temp;
merge(a,b, temp);
for(int i=0; i<temp.size(); i++)
arr[s+i] = temp[i];
}
int main()
{
int n;
cin>>n;
int arr[n];
for(int i=0; i<n; i++) cin>>arr[i];
ms(arr, 0, n-1);
for(int i=0; i<n; i++) cout<<arr[i]<<" ";
cout<<endl;
}