Code outputs random symbols, i'm unsure what is wrong - c++

Question

I've made a program that shortens full names to initials, and removes any spaces between what has been entered. It did work before but now it prints the initials but also random symbols? I can't really figure out why it's doing it. I'm new to programming also.
This is my code:
// This code removes the spaces from the inputted name
char *removeSpaces(char *str)
{
int i = 0, j = 0;
while (str[i])
{
if (str[i] != ' ')
str[j++] = str[i];
i++;
}
str[j] = '\0';
return str;
}
// This code takes the users name, and shortens (sh) it
int main(void) {
char str[100],sh[20];
int j=0;
cout<<"Enter Full Name :";
cin.getline(str,30);
for(int i=0;i<strlen(str);i++)
{
if(i==0){
sh[j]=str[i];
sh[++j]=' ';
}
else if(str[i]==' '){
sh[++j]=str[i+1];
sh[++j]=' ';
}
}
// This then takes the remove spaces code, and prints the initials with a new line
cout << removeSpaces(sh) <<endl;
cout << "\n" <<endl;
return 0;
}
Picture of the output

Answer 1

You are missing adding string terminator character ('\0') to string sh. Below is the program.
#include <stdio.h>
char *removeSpaces(char *str)
{
int i = 0, j = 0;
while (str[i])
{
if (str[i] != ' ')
str[j++] = str[i];
i++;
}
str[j] = '\0';
return str;
}
// This code takes the users name, and shortens (sh) it
int main(void) {
char str[100],sh[100];
int j=0;
cout<<"Enter Full Name :";
cin.getline(str,30);
for(int i=0;i<strlen(str);i++)
{
if(i==0){
sh[j]=str[i];
sh[++j]=' ';
}
else if(str[i]==' '){
sh[++j]=str[i+1];
sh[++j]=' ';
}
}
sh[j+1] = '\0';
// This then takes the remove spaces code, and prints the initials with a new line
cout << removeSpaces(sh) <<endl;
cout << "\n" <<endl;
return 0;
}
Enter Full Name :ra me ge
rmg

Answer 2

You have missed out a line (I guess) after the for loop in your main function, which means your string is potentially not null-terminated.
Using the same (correct) logic you have in your removeSpaces function, just add this line immediately after the for loop in main:
sh[++j] = '\0';

Answer 3

You don't terminate sh with \0 after you're done, yet removeSpaces() expects a null character at the end of the string. Because of this, removeSpaces() could go past your intended boundary.
Just add this line after your for in main():
sh[++j] = '\0\;
Word of warning: You should always make sure that j is < 20 (the size of sh) before you set it. Otherwise, you could go past the boundary of sh. That could also become a source of problems.