how to removing rubbish data(garbage data) from output in c++? - c++

Question

Well, I have to Create class to Insert String in another one at the specific position Without using class string(any pre-made classes except iostream.
When I ask for output it gets rubbish data..
#include "stdafx.h"
#include <iostream>
using namespace std;enter code here
//StrLen Calculates String Length
int StrLen(char *s) {
int len = 0;
while (s[len]!='\0'){
len++;
}
return len;
}
//The value of the string that is it's first argument is inserted into String that is it's second argument, pos is the beginning at position given by main.
char *InsertStr(char *s1, char *s2, int pos) {
int c = 0;
int len1 = StrLen(s1);
int len2 = StrLen(s2);
char s3[100];
int i = pos;
//This while move string from postion till the end of string to s3
while (s1[i] != '\0') {
s3[c] = s1[i];
c++;
i++;
}
c = 0;
i = pos;
//the string in s2[0 to the end of s2] moved to s1[from pos to len1]
while (s2[c] != '\0') {
s1[i] = s2[c];
c++;
i++;
}
int len3 = StrLen(s3);
len1 = StrLen(s1);
int x2 = len1 + len3;
c = 0;
len1 = StrLen(s1);
int x3 = pos + len2;
//this loop get the elements sent to s3 and get them back to
//s1[from pos + len2 till s3[i] reach the end]
for (int i = 0; i < len3; i++) {
s1[x3] = s3[i];
x3++;
}
return s1;
}
int main()
{
char s1[100];
char s2[100];
int pos=0;
cout << "Enter The First Argument String : \n";
cin.getline(s1, 100);
cout << "Enter The Second Argument String : \n";
cin.getline(s2, 100);
cout << "Enter The Position : \n";
cin >> pos;
cout << InsertStr(s1, s2, pos);
cout << "******************";
return 0;
}
I used In cin.getline(), to get all string till '\0'.
I traced the code all loops works fine except last one, Last one have garbage data.
I saw a video on youtube solved it like this but i couldn't trace it..
//This code is a working one, But i didn't use it since i couldn't trace it
#include "stdafx.h"
#include <iostream>
using namespace std;
int strlen(char *s)
{
int c = 0;
while (s[c] != '\0') c++;
return c;
}
char* my_strncat(char *s1, char *s2, int pos)
{
//k= pos
int len1, len2;
int i = 0, k = pos,l=0,j=0;
int x,x1, x2, x3;
len1 = strlen(s1);
len2 = strlen(s2);
char s3[100];
while (i <= len1) {
s3[i] = s1[i];
i++;
}
//x2=len2 j =len1
x1 = len1 + len2;
x3 = len2 + pos;
for (i = pos; i < x1; i++) {
x = s3[i];
if (l < len2) {
s1[i] = s2[l];
l++;
}
s1[x3] = x;
x3++;
}
return s1;
}
int main()
{
char s1[100] ;
char s2[100] ;
int pos = 0;
cout << "Enter The string of Source: \n";
cin.getline(s1,100);
cout << "Enter The string of Destination: \n";
cin.getline(s2, 100);
cout << "Enter The position of Destination: \n";
cin >> pos;
cout << my_strncat(s1, s2, pos) << endl;
return 0;
}

Answer 1

I cannot reproduce your garbage data but I see that you, in InsertStr() systematically forget, to add the zero at the end of strings. Your code goes in UB (Undefined Behaviour) so your garbage data a perfectly explained.
So, copying s1 in s3
while (s1[i] != '\0') {
s3[c] = s1[i];
c++;
i++;
}
s3[c] = '\0'; // add this line!
Copying s2 to s1+pos
while (s2[c] != '\0') {
s1[i] = s2[c];
c++;
i++;
}
s1[i] = '\0'; // add this line!
And copying the last part of s3 at the end of s1
for (int i = 0; i < len3; i++) {
s1[x3] = s3[i];
x3++;
}
s1[x3] = '\0'; // add this line!
Or, maybe, you can simply write your loops, using do/while, as follows
do
s3[c++] = s1[i];
while ( s1[i++] );
// ...
do
s1[i++] = s2[c];
while ( s2[c++] );
// ...
i = 0;
do
s1[x3++] = s3[i];
while ( s3[i++] );