Question

Not sure if I did the mergesort execution correct as well as the merge execution. Can you try explaining it visually sort of like how I was approaching it visually. After that translate it to c++ code if possible. I saw another post that used int *L = new int[n1+1] in the merge function which is the same as int L[n1 +1]correct?

Heres my driver function

int main () € cout << "Enter length you'd like the array Leendl; int size, Aci]; cin » Size ; 1/5 for (int i=0; i< size; it) [ cin >> A[i]; 3115210 Merge sort( A, O, size-1);

Answer 1

Answer : First thing i found out is when you call merge sort first time it divides the array into two sub arrays MergeSort(A,0,2) and MergeSort(A,3,4). What we need to do is execute them concurrently and then combine them through merge function.

As we know that that merge sort is a divide and conquer technique. In which MergeSort() function recursively calls itself to divide the array into two halves until the size become zero and then a Merge() function is called which combines them. I am writing a tree hierarchy of function calls respective to your question follow it for better understanding. Your merge function is correct and it just comparision. I am attaching a c++ implementation with same variable names as yours so it might be easy for you to understand.

SURYA Gold Merge soct 3,4,5,2 10 lo Now merad 1,3,5 2,10 12,3, 5, 10 Pseudo o Size = 5 merge Sort (A, 0, 4); merge Sort (A, 0, 2) Merge Sort (1,0,1) msa, 6212) merge Sort (A, 3, 4) MS (1.3.3) ms (2,44 merge (A, 3.3.4) ako ms (1,0,0) ms (A..., 1), merge (4,0,0,1) merge (1,0,1,2) merge (A,

Activities Text Editor Fri 11:50 Open. A main.cpp Downloads 5 write your code in this editor and press "RUN" button to compile and execute it. Save = 60 7 **** * * * * * * * * * * * * * * * * * * * * * ** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * / 9 #include <iostream> 10 11 using namespace std; 12 13 void Merge(int A[], int p, int x, int q) 14 { int i, j, k; int temp1 = X - P + 1; int temp2 = 9 - X; int left[temp1], right[temp2]; //initializing the above temporary arrays for (i = 0; i < temp1; i++) left[i] = A[P + i]; for (j = 0; j < temp2; j++) right[j] = A[X + 1+ i]; i=0; j=0; k=P; while (i < temp1 && j < temp2) if (left[i] <= right[j]) A[k] = left[i]; i++; else A[k] = right[j]; j++; C++ » Tab Width: 8 Ln 16, Col 18 INS

Activities Text Editor Fri 11:50 main.cpp Downloads Open Save = 20 A[k] = right[j]; j++; IL k++; | O C while (i < temp1) A[k] = left[i]; i++; k++; while (j < temp2) A[k] = right[j]; j++; k++; O << 58 } 59 60 void Merge Sort(int A[], int p, int q) 61 { if(p<q) int x=P+(9-P)/2; Merge Sort(A,P,x); Merge Sort(A, X+1,9); Merge(A,P,X,9); 70 } NW7: 72 int main() 73 { int size; cout<<"Enter the size of array you want to be:"<<endl; cin>>size; N ::: 76 C++ » Tab Width: 8 Ln 16, Col 18 INS

Activities Text Editor Open white < LEMZ) Fri 11:50 main.cpp Downloads Save = 20 54 A[k] = right[j]; j++; k++; 58} 59 60 void Merge Sort(int A[], int p, int q) 61 { if(p<q) int X=p+(-p)/2; Merge Sort(A,P,x); Merge Sort(A,X+1,9); Merge(A,P,X,9); 70 } 72 int main() 73 { int size; cout<<"Enter the size of array you want to be:"<<endl; cin>>size; int A[size]; cout<<"Enter Array Elements"<<endl; for(int i=0;i<size; i++) cin>>A[i]; Merge Sort(A,,size-1); cout<<"Sorted Array is :"<<endl; for(int i=0;i<size; i++) cout<<A[i]<<" "; return 0; 87 88 C++ » Tab Width: 8 Ln 16, Col 18 INS

Enter Array Elements 3 1 5 2 10 Sorted Array is : 1 2 3 5 10

// C++ Implementation of Merge Sort.....................try to test it and have fun
#include <iostream>

using namespace std;

void Merge(int A[],int p,int x,int q)
{
  
int i, j, k;
int temp1 = x - p + 1;
int temp2 = q - x;
  
int left[temp1], right[temp2];
//initializing the above temporary arrays
for (i = 0; i < temp1; i++)
left[i] = A[p + i];
for (j = 0; j < temp2; j++)
right[j] = A[x + 1+ j];
  
  
i=0;
j=0;
k=p;
while (i < temp1 && j < temp2)
{
if (left[i] <= right[j])
{
A[k] = left[i];
i++;
}
else
{
A[k] = right[j];
j++;
}
k++;
}

while (i < temp1)
{
A[k] = left[i];
i++;
k++;
}
while (j < temp2)
{
A[k] = right[j];
j++;
k++;
}
}

void MergeSort(int A[],int p,int q)
{
if(p<q)
{
int x=p+(q-p)/2;
MergeSort(A,p,x);
MergeSort(A,x+1,q);
  
Merge(A,p,x,q);
}
}

int main()
{
int size;
cout<<"Enter the size of array you want to be:"<<endl;
cin>>size;
int A[size];
cout<<"Enter Array Elements"<<endl;
for(int i=0;i<size;i++)
{
cin>>A[i];
}
  
MergeSort(A,0,size-1);
cout<<"Sorted Array is :"<<endl;
for(int i=0;i<size;i++)
cout<<A[i]<<" ";
return 0;
}