what is the issue with this char reverse function? - c++

Question

so I wrote this code to reverse one of the names based on the user option the idea is to use another function to reverse and to use pointers but after trying all I could think of my code return the same name not changed the best I could do was changing the first letter of the name to a weird sign.
#include <iostream>
using namespace std;
void reverse(char* A) {
int count = 0;
char temp[10];
for (int i = 0; A[i] != NULL; i++)
count++;
for (int i = 0; A[i] != NULL; i++) {
temp[count]=A[i];
count--;
}
for (int i = 0; A[i] != NULL; i++) {
A[i] = temp[i];
}
}
int main(){
int x= 0;
int index;
char Name_list[5][10];
cout << "please enter the names of the student " << endl;
for (int i = 0; i < 5; i++) {
cin >> Name_list[i];
for (int j = 0; Name_list[i][j] != NULL; j++) {
x++;
}
while (x > 10)
{
x = 0;
cout << "you have entered more then the allowed number of characters per name enter another name " << endl;
cin >> Name_list[i];
for (int j = 0; Name_list[i][j] != NULL; j++) {
x++;
}
}
x = 0;
}
for (int i = 0; i < 5; i++) {
cout << Name_list[i] << endl;
}
cout << "please enter the index of the name you want to reverse" << endl;
cin >> index;
while (index>4||index <0)
{
cout << "you entered incorrect index please enter a number from 0 to 4 " << endl;
}
reverse(Name_list[index]);
for (int i = 0; i < 5; i++) {
cout << Name_list[i] << endl;
}
system("pause");
}

Answer 1

For starters such a function should return a pointer to the result string. That is it should be declared like
char * reverse( char *s );
Note: do not use variable names consisting from upper case letters.
The type int can be not large enough to store length of a string. Instead use the type size_t.
char * reverse( char *s )
{
size_t count = 0;
//...
It is totally unclear why there is present an array with the number of elements equal to the magic number 10
char temp[10];
To reverse a string there is no need to declare an auxiliary array. Such an approach is principally wrong.
In this for loop
for (int i = 0; A[i] != NULL; i++)
there is compared an object of the type char with the pointer NULL. The compiler should issue a message for such a wrong comparison. It seems you mean
for (int i = 0; A[i] != '\0'; i++)
In any case the introduced variable i in this first for loop is redundant because you already has the variable count.
As you have the array temp with the fixed size equal to 10 then the both loops after the first loop can invoke undefined behavior even if the length of the source string is equal exactly to 10.
And the result string is not zero terminated.
The function can look the following way.
char * reverse( char *s )
{
size_t count = 0;
while ( s[count] ) ++count;
for ( size_t i = 0; i < count / 2; i++ )
{
char c = s[i];
s[i] = s[count - i - 1];
s[count - i - 1] = c;
}
return s;
}
Or using standard functions you could write the function reverse the following way
#include <utility>
#include <cstring>
//...
char * reverse( char *s )
{
for ( size_t i = 0, n = std::strlen( s ); i < n / 2; i++ )
{
std::swap( s[i], s[n-i-1] );
}
return s;
}
Pay attention to that there is the standard algorithm std::reverse. Using it you could reverse a string the following way
std::reverse( s, s + std::strlen( s ) );

Answer 2

for (int i = 0; A[i] != NULL; i++) {
temp[count]=A[i];
count--;
}
If i goes up from 0 to 5, count goes down from 6 to 1.

Answer 3

Ok, a few things.
If you want do some string manipulation, look into the stdlib. Unless you are doing this for class.
Your writing everything to the end of the temp. buffer
You need to add an extra character at the end of the strings for the null byte (I think this implementation may allow for a seg. fault)