programming-examples/c++/Combinational_Problems/C++ Program to Implement Merge Sort.cpp

/*
 * C++ Program to Implement Merge Sort
 */
#include <iostream>
using namespace std;
#include <conio.h>
void merge(int *,int, int, int );
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 merge(int *a, int low, int high, int mid)
{
    int i, j, k, c[50];
    i = low;
    k = low;
    j = mid + 1;
    while (i <= mid && j <= high)
        {
            if (a[i] < a[j])
                {
                    c[k] = a[i];
                    k++;
                    i++;
                }
            else
                {
                    c[k] = a[j];
                    k++;
                    j++;
                }
        }
    while (i <= mid)
        {
            c[k] = a[i];
            k++;
            i++;
        }
    while (j <= high)
        {
            c[k] = a[j];
            k++;
            j++;
        }
    for (i = low; i < k; i++)
        {
            a[i] = c[i];
        }
}
int main()
{
    int a[20], i, b[20];
    cout<<"enter  the elements\n";
    for (i = 0; i < 5; i++)
        {
            cin>>a[i];
        }
    mergesort(a, 0, 4);
    cout<<"sorted array\n";
    for (i = 0; i < 5; i++)
        {
            cout<<a[i];
        }
    cout<<"enter  the elements\n";
    for (i = 0; i < 5; i++)
        {
            cin>>b[i];
        }
    mergesort(b, 0, 4);
    cout<<"sorted array\n";
    for (i = 0; i < 5; i++)
        {
            cout<<b[i];
        }
    getch();
    /*
     * C++ Program to Implement Merge Sort
     */
#include <iostream>
    using namespace std;
#include <conio.h>
    void merge(int *,int, int, int );
    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 merge(int *a, int low, int high, int mid)
    {
        int i, j, k, c[50];
        i = low;
        k = low;
        j = mid + 1;
        while (i <= mid && j <= high)
            {
                if (a[i] < a[j])
                    {
                        c[k] = a[i];
                        k++;
                        i++;
                    }
                else
                    {
                        c[k] = a[j];
                        k++;
                        j++;
                    }
            }
        while (i <= mid)
            {
                c[k] = a[i];
                k++;
                i++;
            }
        while (j <= high)
            {
                c[k] = a[j];
                k++;
                j++;
            }
        for (i = low; i < k; i++)
            {
                a[i] = c[i];
            }
    }
    int main()
    {
        int a[20], i, b[20];
        cout<<"enter  the elements\n";
        for (i = 0; i < 5; i++)
            {
                cin>>a[i];
            }
        mergesort(a, 0, 4);
        cout<<"sorted array\n";
        for (i = 0; i < 5; i++)
            {
                cout<<a[i];
            }
        cout<<"enter  the elements\n";
        for (i = 0; i < 5; i++)
            {
                cin>>b[i];
            }
        mergesort(b, 0, 4);
        cout<<"sorted array\n";
        for (i = 0; i < 5; i++)
            {
                cout<<b[i];
            }
        getch();
    }
    /*
    Output
    enter  the elements
    78
    45
    80
    32
    67
    sorted array
    32
    45
    67
    78
    80