Problem solving using mearge sort

problem_8.5_1.cpp

/**
WAP that takes 2 sorted (in non-increasing order) integer arrays as input, then merges the two arrays into one array sorted in non-increasing order in O(n+m). 

Sample input                  Sample output
4
5 3 2 1
5
7 6 3 2 1                     7 6 5 3 3 2 2 1 1


5
6 4 3 2 1
3
6 4 0                         6 6 4 4 3 2 1 0
**/

#include <bits/stdc++.h>
using namespace std;

vector<int> mergeSort(vector<int> a, vector<int> b, vector<int> c)
{
    if(a.size() <= 1)
    {
        return a;
    }
    
    vector<int>sorted_a;
    int idx1 = 0;
    int idx2 = 0;
    int size = a.size();
    
    
    for(int i = 0; i < size; i++)
    {
        if(idx1 == b.size()) {
            sorted_a.push_back(c[idx2]);
            idx2++;
        } else if(idx2 == c.size()) {
            sorted_a.push_back(b[idx1]);
            idx1++;
        } else if(b[idx1] > c[idx2])
        {
            sorted_a.push_back(b[idx1]);
            idx1++;
        } else {
            sorted_a.push_back(c[idx2]);
            idx2++;
        }
    }
    
    return sorted_a;
}

int main() {
    int n;
    cin >>n;
    vector<int> b(n);
    
    for(int i = 0; i< n; i++)
    {
        cin >>b[i];
    }
    
    int m;
    cin >> m;
    vector<int> c(m);
    
    for(int i = 0; i< m; i++)
        cin >> c[i];
    
    vector<int> array(n+m);
    
    vector<int> ans = mergeSort(array, b, c);
    
    for(int i = 0; i < ans.size(); i++)
        cout << ans[i] <<" ";
    
    return 0;
    
}