Access Violation----Why is that?

[stealwings]

I have implemented a binary search and some other functions to my code, when I compile it, it gives me no error, but when I run it, it gives me an Access violation, why? Can some one explain me plz. Thanks in advance.

// SpanishBreakPredict.cpp : Defines the entry point for the console application.
//
 
#include "stdafx.h"
#include <iostream>
using namespace std;
#include <fstream>
using std::ifstream;
using std::ofstream;
#include <stdio.h>
#include <cstdlib>
#include <string>
#include <stdlib.h>
#include <iomanip>
#include <vector>
#define MAXLENGTH 1000
 
 
int wmain(int argc, wchar_t * argv[], wchar_t *envp[])
{
    char WordCount[MAXLENGTH];        //Temp array to save input file words for lenght calculation
    char MyWord[MAXLENGTH];            //Temp array to save input file words.
    char MyStandard[MAXLENGTH];        //Temp array to save the standard words list
//    vector<string> MyWords;            // Vector to hold input file.
//    vector<string> Standard;        // Vector to hold Text-normalization-phrases
    ifstream CountStandard;
    ifstream CountInput;
    ifstream ReadWord;
    ifstream ReadStandard;
    ofstream WriteWord;
 
/**********************To get number of characters of each line****************************/
    int StandardSize=0;
    CountStandard.open("Standard.txt");
    while(!CountStandard.eof()&&CountStandard.getline(WordCount, MAXLENGTH))
    {
        StandardSize++;
    }
//    cout<<StandardSize<<endl;
    CountStandard.close();
    vector<string> Standard(StandardSize);
    int InputSize=0;
    CountInput.open("file.txt");
    while(!CountInput.eof()&&CountInput>>WordCount)//CountInput.getline(WordCount, MAXLENGTH))
    {
        InputSize++;
    }
    cout<<InputSize<<endl;
    vector<string> MyWords(InputSize);
 
/**************************************************************************************/
    WriteWord.open("file.dat",ios::app);
    if(!WriteWord.is_open())
    {
        cerr<<"couldn't create file"<<endl;
        exit(1);
    }
    ReadStandard.open("Standard.txt");    
    if (!ReadStandard)
    {
        cerr<<"Standard text file not found."<<endl;    
        exit (1);
    }
 
 
    while(!ReadStandard.eof())                        //read the file till reaches the end.
    {
 
        ReadStandard.getline(MyStandard,MAXLENGTH);      // read a line from the file.
                                                     //    (one line is a phrase)
        Standard.push_back(MyStandard);    //push the phrase into the vector "Standard";
 
    }                                                //read standard words over
    /*for(unsigned i=0; i<Standard.size();i++)
        {
            cout<<Standard[i]<<endl;
        }*/
    ReadStandard.close();//close the file handle;
 
 
    ReadWord.open("file.txt");
    if (!ReadWord)
    {
        cerr<<"input file not found please ensure it exist."<<endl;
        exit (1);
    }
 
 
    while(ReadWord>>MyWord)
    {
    //    cout<<MyWord<<endl;    
    //    ReadWord>>MyWord;
    //    ReadWord.getline(MyWord,MAXLENGTH);
        MyWords.push_back(MyWord);    
    }
 
/*******************************To print holding words of vector**********************/
/*    for(int i=0; i<MyWords.size(); i++)
    {
        cout<<MyWords[i]<<endl;
    }*/
/**************************************************************************************/
    ReadWord.close();
    WriteWord.close();
 
/**************************************************************************************/
/*                    SEARCH AND COMPARE, THEN REPLACE IF MATCH IS TRUE.                */
/*                        Note: This part does a linear search                          */
/**************************************************************************************/
/*    for(unsigned i=0;i<Standard.size();i++) 
    {
 
        for(unsigned j=0;j<MyWords.size();j++)  //each MyWords compare to the Standard 
                                                //and see if it is in the standard vector
        {
            string::size_type FoundAt=MyWords[i].find(Standard[j]);
            while( string::npos != FoundAt )
                {
                    MyWords[i].replace( FoundAt, Standard[j].length(),Standard[j]+"/");
                    //cout<< MyWords[i]<< endl;
                    FoundAt = MyWords[i].find( Standard[j], FoundAt + Standard[j].length() );
                }
 
            //if(MyWords[i]==Standard[j])            // if it equal to one of the words in the standard vector 
            //    MyWords[i]=MyWords[i]+"/";            // add the slash to the end;
        }
 
    }*/
 
 
/*********************************************************************************************/
/*                                    BinarySearch                                              */
/*********************************************************************************************/
int first=0, last, mid;
while(Standard[first]<=Standard[last])
{
    Standard[mid]=Standard[(first+last)/2];
    for (int i=0; i<MyWords.size(); i++)
    {
        if(MyWords[i]<Standard[mid].substr())
            first=mid+1;        
 
    }
}
/***********************************Create output file****************************************/
/*    for(unsigned j=0;j<MyWords.size();j++)        // for each word in MyWords vector  
    {
        WriteWord<<MyWords[j]<<endl;            // write it to the destination file
    }
    WriteWord.flush();                            // flush the memory to ensure all is written to the file
    WriteWord.close();    */                        // close the write file handls
    return 0;
}
 

THAT IS MY CODE AND THIS IS THE PART THAT IS GIVING ME TROUBLE

int first=0, last, mid;
while(Standard[first]<=Standard[last])
{
    Standard[mid]=Standard[(first+last)/2];
    for (int i=0; i<MyWords.size(); i++)
    {
        if(MyWords[i]<Standard[mid].substr())
            first=mid+1;        
 
    }
}

[stealwings]

Sorry for the trouble, I already realized that it was a logical problem, it is solved, but I got this new problem, I have the part of the code as follow:

int first=0;
int last= StandardSize-1;
int mid=(first+last)/2;
//cout<<MyWords.size()<<endl;
    for (int i=0; i<MyWords.size();i++)
    {
        while(first<=last)
        {
            if(MyWords[i]>Standard[mid].substr())
                first=mid+1;
            else if(MyWords[i]<Standard[mid].substr())
                last=mid-1;
            else 
                cout<<Standard[mid]<<endl;
        }
        cout<<"Not found"<<endl;
        return -1; 
    }
 

it gives me an infinite loop of blank spaces, why?