duplicate name checking function for an array - c++

Question

I am still a beginner in C++, so I'm sorry if the question is simple.
I am trying to build a program that asks you to input names and register them to an array. Then, I need to call a function to check if there are any duplicate names. If there are any, it asks the user to input another name.
The problem I'm having is that the function is called whether or not there are duplicates, and always replaces the first name that was entered.
int checking(string stringArray[5]) {
int i, z ;
for (i = 0; i < 5; i++) {
for (z = 0; z < 5; z++) {
if (z != i) { // Makes sure don't check number against itself
if (stringArray[z] == stringArray[i]) {
return i;
}
else {
return 0;
int main(){
for (i = 0; i < 5; i++) {
cin >> stringArray[i];
}
j = checking(stringArray);
if (j == 0) {
cout << "Please re-enter name " << ". Duplicate names are not allowed"
<<'\n';
cin >> stringArray[j];
}

Answer 1

Some observations (ignoring the syntax errors, I assume these are not present in your actual code):
z doesn't need to start at 0 every time, it can start at i + 1 because you dont need to check pairs you have already checked (makes it simpler and runs faster)
you don't want to return in your loop, it will prevent you from checking past the first repeated name. Instead move your reenter statement into the loop.
generally you dont want to use literals (5) in a loop, instead use a variable to store the length of the array and compare to that (this is just a general programming rule, it won't change how the code runs)
Your final checking() function should look closer to:
void checking(string stringArray[5]) {
int i, z ;
// consider replacing 5 with a variable
for (i = 0; i < 5; i++) {
for (z = i+1; z < 5; z++) {
if (stringArray[z] == stringArray[i]) {
cout << "Please re-enter name " <<
". Duplicate names are not allowed" <<'\n';
cin >> stringArray[z];
/* restart the loop user may have entered a */
/* second duplicate from previous entries */
i = 0;
z=i+1;
}
}
}
}