Merge Sort

[computerfox]

Hello everyone,

I'm having some trouble with the code for merge sort. I get what is it but the code doesn't seem to work. Here is my code:

////.h

#include <iostream>
#include <string>
using namespace std;


string merge(string,string);
string mergeSort(string);
string rest(int,int,string);

string rest(int from,int to,string phrase){
	string temp;
	
	for(int i=from;i<=to;i++){
		temp[i-1]=phrase[i];
	}
	return temp;
}
string merge(string left,string right){
	string result;
* * while (left.length() > 0 || right.length() > 0){
* * * * if (left.length() > 0 && right.length() > 0){
			if (left[0] <= right[0]){
* * * * * * * * result+=left[0];
* * * * * * * * left= rest(1,left.length(),left);
			}
			if(left[0]>right[0])
			* * {
				result+=right[0];
				right= rest(1,right.length(),right);
			}
				if (left.length() > 0){
					result+= left[0];
					left= rest(1,left.length(),left);
				}
				if (right.length() > 0){
					
				* * result+=right[0];
					right= rest(1,right.length(),right);
				}
			}
		}
	return result;	
}
string mergeSort(string a){
	if(a.length()<=1)
		return a;
	
	string left,right,result;
	int middle=(a.length())/2;
	
	for(int i=0;i<a.length();i++){
		if(i<middle)
		* left+=a[i];
		else*
			if(i>=middle)
			right+=a[i];

	}
	left = mergeSort(left);
* * right = mergeSort(right);
* * result = merge(left, right);
* * return result+left;
}

	


////.cpp

#include "mergeSort.h"
using namespace std;

int main () {
* * string a,b;
	int again=1;
	while(again==1){
		
	* * cout<<"Enter string to sort: ";
	* * cin>>a;		
		cout<<"Before the sort: "<<a<<endl;
		cout<<"After sort: ";
		cout<<mergeSort(a)<<endl;
	* * cout<<"1-Again* 2-Close: ";
		cin>>again;
	}
	
* * return 0;
}

Any ideas?

[computerfox]

Easy fix-

////.h

#include <iostream>
#include <string>
using namespace std;

char *mergeSort(char letters[], char temp[], int array_size);
char *mSort(char letters[], char temp[], int left, int right);
char *merge(char letters[], char temp[], int left, int mid, int right);

char *mergeSort(char letters[], char temp[], int array_size)
{
    return mSort( letters, temp, 0, array_size - 1);
}


char *mSort(char letters[], char temp[], int left, int right)
{
    int mid;
    
    if (right > left)
    {
        mid = (right + left) / 2;
        mSort( letters, temp, left, mid);
        mSort( letters, temp, (mid+1), right);
        
        merge( letters, temp, left, (mid+1), right);
    }
    
    return letters;
}

char *merge(char letters[], char temp[], int left, int mid, int right)
{
    int i, leftEnd, elements, tmpPos;
    
    leftEnd = (mid - 1);
    tmpPos = left;
    elements = (right - left + 1);
    
    while ((left <= leftEnd) && (mid <= right))
    {
        if ( letters[left] <=  letters[mid])
        {
            temp[tmpPos] =  letters[left];
            tmpPos += 1;
            left += 1;
        }
        else
        {
            temp[tmpPos] =  letters[mid];
            tmpPos += 1;
            mid += 1;
        }
    }
    
    while (left <= leftEnd)
    {
        temp[tmpPos] =  letters[left];
        left += 1;
        tmpPos += 1;
    }
    while (mid <= right)
    {
        temp[tmpPos] =  letters[mid];
        mid += 1;
        tmpPos += 1;
    }
    
    for (i=0; i < elements; i++)
    {
        letters[right] = temp[right];
        right -= 1;
    }
    
    return temp;
}


////.cpp


#include "mergeSort.h"

int main()
{
    int max,again=1;
    
    while(again==1){
    cout<<"Word size: ";
    cin>>max;

    char arrayOne[max];
    char arrayTwo[max];
        string result;
        
    cout<<"Enter word to sort: ";

    //Enter character array
    for(int i=0;i<max;i++){
        cout<<"Letter"<<i+1<<"/"<<max<<": ";
        cin>>arrayOne[i];
    }
   
    //Before the sort    
    cout<<"Before the sort: ";
    for(int i=0;i<max;i++)
        cout<<arrayOne[i]<<" ";
    cout<<endl;
    
    //Sort
	result=mergeSort(arrayOne, arrayTwo, max);
    
	//After the sort
    
    cout<<"After the sort: ";
    for(int i=0;i<max;i++)
        cout<<result[i]<<" ";
    cout<<endl;
    
        cout<<"1-Again  2-Close: ";
        cin>>again;
    }
    
    cout<<endl;
	return 0;
}

Merge sort can not be done with strings, you need a list of either characters or arrays. Despite strings being character arrays, it treats it differently.