Помогите найти ошибку

#include "stdafx.h"
#include <string.h>
#include <stdlib.h>
#include <iostream.h>
#include <conio.h>
#include <iomanip.h>
#include <stdio.h>


class STRING
{
char *line;
int len;
public:
STRING();
STRING(char*);
STRING(const STRING &);
~STRING();
void print();
void input_string(char *);
void change();
};
STRING::STRING()
{
line=new char[256];
if(!line)
cout << "Memory error!" << endl;
for(int i=0;i<255;i++)
line[i]=0;
len=strlen(line);
cout<<"WORKING CONSTRUCTOR WITHOUT PARAMETERS"<<endl;
}
STRING::STRING(char *ln)
{
len = strlen(ln);
line=new char[len+1];
if(!line)
cout << "Memory error!" << endl;
strcpy(line,ln);
cout<<"WORKING CONSTRUCTOR WITH PARAMETERS"<<endl;
}
STRING::STRING(const STRING &obj)
{
len = obj.len;
line = new char [len + 1];
if(!line)
cout << "Memory error!" << endl;
strcmp(line, obj.line);
cout<<"Rabotaet konstruktor generator kopij"<<endl;

}
STRING::~STRING()
{
delete []line;
cout<<"WORKING DESTRUCTOR"<<endl;
}
void STRING::print()
{
cout<<line<<endl;
cout<<len<<endl;
}
void STRING::input_string(char * s)
{
delete []line;
len = strlen(s);
line = new char[len+1];
if(!line)
cout << "Memory error!" << endl;
strcpy(line, s);

}
void STRING::change()
{
int num = 0, tmp_len1, tmp_len2, k=0;
char ln1[80], *ln2, *ln3;
cout<<"Input word"<<endl;
cin>>ln1;
tmp_len1 = strlen(ln1);
while((line[k]!=' ') && (k<=len))
{
num=k;
k++;
}
ln2 = new char[len-num+1];
if(!ln2)
cout << "Memory error!" << endl;
for(int i=0;i<(len-num);i++)
ln2[i]=line[i+num+1];
tmp_len2 = strlen(ln2);
cout<<tmp_len2<<endl;
len = tmp_len1 + tmp_len2;
ln3 = new char[len+1];
if(!ln3)
cout << "Memory error!" << endl;
for(i=0; i<len; i++)
{
if(i<tmp_len1)
ln3[i] = ln1[i];
else
ln3[i] = ln2[i-tmp_len1];
}
delete []line;
line = new char[len+1];
if(!line)
cout << "Memory error!" << endl;
strcpy(line, ln3);
delete []ln2;
}
int main()
{
STRING ptr;
char tmp[256];
cout<<"enter"<<endl;
gets(tmp);
ptr.input_string(tmp);
ptr.print();
ptr.change();
ptr.print();
_getch();
return 0;
}