for (int k = start; k < end; k++)
{
    if (L.at(x) <= R.at(y))
    {
        v.at(k) = L.at(x);          // out of bounds
        x++;
    }
    else
    {
        v.at(k) = R.at(y);          // out of bounds
        y++;
    }

}

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <algorithm>

using namespace std

vector<string> readFile(string fileName) {
    /* reads a textfile into vector. Works dandy. */ }

vector<string> merge(vector<string>& v, int start, int mid, int end)
{
int n1 = mid - start + 1;
int n2 = end - mid;

vector<string> L;
vector<string> R;

L.resize(n1 + 1); // size left vector
R.resize(n2 + 1); // size right vector

for (int i = 1; i < n1; i++) {
    L.at(i) = v.at(start + i - 1); // populate left vector
}
for (int j = 1; j < n2; j++) {
    R.at(j) = v.at(mid + j);       // populate right vector
}

int x = 1;
int y = 1;

for (int k = start; k < end; k++)
{
    if (L.at(x) <= R.at(y)) {
        v.at(k) = L.at(x);          // merge left vector into v
        x++;
    }
    else{
        v.at(k) = R.at(y);          // merge right vector into v
        y++;
    }

}
return v;
}
vector<string> mergeSort(vector<string>& v, int start, int end)
{
int middle;
if (start < end)                    // base case
{
    middle = (start + end) / 2;     // find middle
    mergeSort(v, start, middle);    // divide vectors
    mergeSort(v, middle + 1, end);
    merge(v, start, middle, end);   // merge sorted vectors
}
return v;
}
int main() {
vector<string> vectorReadIn;
vector<string> sortedVector;
int x = 0;

string fileName = "C:/Users/User/Downloads/Algorithims/Perm Words/perm15k.txt";

vectorReadIn = readFile(fileName);    // reads file into vector

sortedVector = mergeSort(vectorReadIn, 1, vectorReadIn.size());  // calls mergesort
cout << "Sorted file:" << endl;
while (x < 8) {
    cout << sortedVector.at(x);
    x++; }
}