Overload the Logical Operators to Sort Strings Alphabetically

In c++, we have function like strcmp(const char* c1,const char* c2) to help us decide which is alphabetically before the other. Yet we still want to use a more easy-going function as a bool operator < or something else like other logical operators.

And here we have a customized user-define class String, which is incomplete due this is only for demonstration of overloading operators.

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

class String{

	char* chars;

public:

	int length;

	String String::operator =(const char* r){
		length=strlen(r);
		chars=(char*)malloc((length+1)*sizeof(char));
		for(int i=0;i<=length;i++){
			this->chars[i]=r[i];
		}
		return *this;
	}

	String String::operator =(String r){
		length=r.length;
		chars=(char*)malloc((length+1)*sizeof(char));
		for(int i=0;i<=length;i++){
			this->chars[i]=r[i];
		}
		return *this;
	}

	char &String::operator [](int idx){
		return chars[idx];
	}

	bool operator <(String r)
	{
		for(int idx=0;idx<=(length<r.length?length:r.length);idx++)
		{
			if(tolower(chars[idx])<tolower(r[idx]))
				return true;
			else
				if(tolower(chars[idx])>tolower(r[idx]))
					return false;
				else
					continue;
		}
		return false;
	}

	bool operator >(String r)
	{
		return r<*this;
	}

	bool operator ==(String r)
	{
		return !(*this>r)&&!(*this<r);
	}

	bool operator !=(String r)
	{
		return !(*this==r);
	}

	bool operator <=(String r)
	{
		return !(*this>r);
	}

	bool operator >=(String r)
	{
		return !(*this<r);
	}

	friend ostream&operator <<(ostream &os,String &right);

	friend istream&operator <<(istream &is,String &right);

	String(int n){
		length=n;
		chars=new char[length];
	}

	String (){
		length=0;
	}

	String (const char* cs){
		*this=cs;
	}

};

ostream & operator<<(ostream &os,  String &right)
{
	for(int i=0;i<=right.length;i++)
	{
		os<<right[i];
	}

	return os;
}

istream & operator>>(istream &is,String &right)
{
	int idx=2;
	char* tmpcs=new char[idx];
	char c;
	int i=0;
	for(;;i++)
	{
		c=is.get();
		if(c!='n')
		{
			if(i>=idx)
			{
				idx=i+1;
				tmpcs=(char*)realloc(tmpcs,idx*sizeof(char));
			}
			if(isalpha(c))
			{
				tmpcs[i]=c;
			}

		}
		else
		{
			if(i>=idx)
			{
				idx=i+1;
				tmpcs=(char*)realloc(tmpcs,idx*sizeof(char));
			}
			tmpcs[i]='';
			break;
		}
	}
	right=tmpcs;
	return is;

}

template <typename T>
void sort(T *source,int startidx,int endidx)
{
	for(int i=startidx+1;i<=endidx;i++)
	{
		for(int j=startidx;j<i;j++)
		{
			if(source[i]<source[j])
			{
				T key=source[i];
				for(int k=i;k>j;k--)
				{
					source[k]=source[k-1];
				}
				source[j]=key;
				break;
			}
		}
	}
}
int main()
{
	String group[5];

	cout<<"Please input 5 words"<<endl;
	for(int i=0;i<5;i++)
	{
		cin>>group[i];
	}
	sort(group,0,4);
	cout<<"after the sorting"<<endl;
	for(int i=0;i<5;i++)
	{
		cout<<group[i]<<endl;
	}
	system("pause");
	return 0;
}