Set function in c++ not working [closed] - c++

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Im writing a Set class in c++(i know there is already a library this is an assignment) and similar to the one in C++ im writing a function to check if the entry being inputted is already in the set
void Set::insert(const Set::value_type& entry)
{
for (int i=0; i<used;i++)
{
if(data[i]!=entry && used<CAPACITY)
{
data[used] = entry;
used++;
}
else
{
throw "Out of capacity in Set and Intger already in Set";
}
}
}
What the function does is look if the number is in the set. If the number is not in the set and if used < capacity (meaning their is still room) then the number is inserted. When i use the insert function nothing happens. Could someone help me out. Maybe im approaching this the wrong way.

Answer 1

As written, when insert-ing to an empty Set, used will be 0, so the loop terminates without doing anything. You don't handle the case where the value wasn't found after the loop, so it never inserts.
Even if you switched to loop to CAPACITY, the inner check is going to fill the whole Set with the same value on first run (because the if check's block executes, but doesn't break the loop, so it stores the same value over and over until it fills the Set or finds itself), then on subsequent inserts, it will immediately raise an exception for being full. Perhaps you wanted something like this?
void Set::insert(const Set::value_type& entry)
{
// If you have a membership test function, you can reuse it here instead
// of including this loop, e.g.:
// if (this->contains(entry)) return;
for (int i=0; i < used;i++)
{
if (data[i] == entry) {
// value already in set, nothing to do
return;
}
}
// Not already in Set, add if we have room or raise exception
if (used < CAPACITY) {
data[used++] = entry;
return;
}
throw "Out of capacity in Set";
}

Answer 2

When the set is initially empty, so that used == 0, your loop doesn't do anything, because the i < used condition fails immediately. So you never add the new item to the set.
And if there are items in the set, the loop adds the new entry to the set if it's different from any existing element. It adds it repeatedly for each element that it's not equal to.
What you need to do is go through the entire set, and see if a match is found anywhere. If it makes it through the entire loop without finding a match, it adds the new entry.
void Set::insert(const Set::value_type& entry)
{
for (int i=0; i<used;i++)
{
if(data[i] ==entry)
{
return;
}
}
// Not found, add it
if (used < CAPACITY) {
data[used++] = entry;
} else
{
throw "Out of capacity in Set";
}
}