String subscript out of range error "C++" - c++

Question

This program takes a text file and changes each word into pig Latin. I have gotten everything to work but continue to get the error "subscript out of range". I have tried to change many things but cant get it to go away. Can someone explain why I am getting this error?
#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>
using namespace std;
void piglatin ( string word[], string temp, ifstream & in, int num);
int main()
{
string word[300];
string original[300];
string temp;
ifstream in;
int i=0,
j=0,
x=0,
par=0,
length=0;
in.open("text.txt");
if (in.is_open()) { //Checks if file is open
cout << "\nFile is open....\n\n\n";
} else {
cout << "Error: Failed to open!\n";
cout << "Exiting program\n";
exit(-1);
}
cout<<"Original text\n\n";
do {//Continues while loop until no more input.
in >> original[x];
cout << original[x] << " ";
x++;
par = par + x;
} while (!in.eof());
cout<<"\n\n";
cout<<"Pig Latin\n\n";
piglatin(original,temp,in,par);
return 0;
}
void piglatin ( string word[], string temp, ifstream & in, int num)
{
int i=0, length, j=0,a=0;
for(j = 0; j < num; j++) {
string str (word[j]);
length = str.size();
temp[0] = word[j][0];
if ((temp[0] == 'a') ||
(temp[0] == 'e') ||
(temp[0] == 'i') ||
(temp[0] == 'o') ||
(temp[0] == 'u'))
{
word[j] += "way";
} else {
for(i = 0; i <= length-1; i++) {
word[j][i] = word[j][i+1];
}
word[j][length-1] = temp[0];
word[j] += "ay";
}
cout << word[j] << " ";
length = 0;
}
cout << "\n\n";
}

Answer 1

This statement
temp[0] = word[j][0];
is invalid because string temp is empty and you may not use the subscript operator with empty strings to store a character.
You could write before the for loop for example
temp.resize( 1 );
Also I do not see any sense in the parameter temp. Instead of string temp you could use in the function local variable char temp; because you are using temp only to store one character.

Answer 2

I believe you are missing a parameter to the ifstream: The ifstream object requires two parameters, a filename and a mode which describes the requested i/o mode for the file.
in.open("text.txt");
Should be:
in.open("text.txt", ifstream::in);
Here is a link to the API for ifstream.open:
http://www.cplusplus.com/reference/fstream/ifstream/open/