Merge Sort in C++

Welcome to the Merge Sort in C++ page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

#include <iostream>
#include <bits/stdc++.h>

using namespace std;

void handle_error()
{
    cout << "Usage: please provide a list of at least two integers to sort in the format \"1, 2, 3, 4, 5\"" << endl;
    exit(0);
}

int check(string s)
{
    int x1 = 0, x2 = s.size() - 1;

    for (int i = 0; i < s.size(); i++)
    {
        if (s[i] != ' ')
        {
            x1 = i;
            break;
        }
    }

    for (int i = s.size() - 1; i >= x1; i--)
    {
        if (s[i] != ' ')
        {
            x2 = i;
            break;
        }
    }

    for (int i = x1; i <= x2; i++)
    {
        if (s[i] == ' ')
        {
            handle_error();
        }
    }

    return stoi(s);
}

vector<int> convert(string s)
{

    vector<int> v;
    string num = "";
    for (int i = 0; i < s.size(); i++)
    {
        if ((int)s[i] >= 48 && (int)s[i] <= 57 || s[i] == ' ')
        {
            num += s[i];
        }
        else if (s[i] == ',')
        {
            v.push_back(check(num));
            num = "";
        }
        else
        {
            handle_error();
        }
    }

    if (num.size() > 0)
    {
        v.push_back(check(num));
    }

    return v;
}

void merge(int low, int mid, int high, vector<int> &v)
{
    int n1 = mid - low + 1;
    int n2 = high - mid;

    vector<int> v1(n1), v2(n2);

    for (int i = 0; i < n1; i++)
    {
        v1[i] = v[i + low];
    }

    for (int i = 0; i < n2; i++)
    {
        v2[i] = v[i + mid + 1];
    }

    int j = 0, k = 0;
    int l = low;

    while (j < n1 && k < n2)
    {
        if (v1[j] < v2[k])
        {
            v[l] = v1[j];
            j++;
        }
        else
        {
            v[l] = v2[k];
            k++;
        }
        l++;
    }

    while (j < n1)
    {
        v[l] = v1[j];
        j++;
        l++;
    }

    while (k < n2)
    {
        v[l] = v2[k];
        k++;
        l++;
    }
}

void mergesort(int low, int high, vector<int> &v)
{

    if (low < high)
    {
        int mid = (low + high) / 2;
        mergesort(low, mid, v);
        mergesort(mid + 1, high, v);
        merge(low, mid, high, v);
    }
}

int main(int argc, char *argv[])
{

    if (argc < 2)
    {
        handle_error();
    }

    vector<int> v = convert(argv[1]);

    if (v.size() < 2)
    {
        cout << "Usage: please provide a list of at least two integers to sort in the format \"1, 2, 3, 4, 5\"" << endl;
        exit(0);
    }

    int n = v.size();
    int min_idx;

    mergesort(0, n - 1, v);

    for (int i = 0; i < n - 1; i++)
    {
        cout << v[i] << ", ";
    }
    cout << v[n - 1];
}

Merge Sort in C++ was written by:

• Jeremy Grifski
• Sailok Chinta

If you see anything you'd like to change or update, please consider contributing.

Note: The solution shown above is the current solution in the Sample Programs repository as of Oct 10 2022 16:05:09. The solution was first committed on Oct 26 2019 08:19:51. As a result, documentation below may be outdated.

How to Implement the Solution

No 'How to Implement the Solution' section available. Please consider contributing.

How to Run the Solution

No 'How to Run the Solution' section available. Please consider contributing.