Using a function to remove duplicates from an array in C++ - c++

Question

I'm writing a program that has a user input integers into an array, calls a function that removes duplicates from that array, and then prints out the modified array. When I run it, it lets me input values into the array, but then gives me a "Segmentation fault" error message when I'm done inputing values. What am I doing wrong?
Here is my code:
#include <iostream>
using namespace std;
void rmDup(int array[], int& size)
{
for (int i = 0; i < size; i++)
{
for (int j = i + 1; j < size; j++)
{
if (array[i] == array[j])
{
array[i - 1 ] = array[i];
size--;
}
}
}
}
int main()
{
const int CAPACITY = 100;
int values[CAPACITY], currentSize = 0, input;
cout << "Please enter a series of up to 100 integers. Press 'q' to quit. ";
while (cin >> input)
{
if (currentSize < CAPACITY)
{
values[currentSize] = input;
currentSize++;
}
}
rmDup(values, currentSize);
for (int k = 0; k < currentSize; k++)
{
cout << values[k];
}
return 0;
}
Thank you.

Answer 1

for (int i = 0; i < size; i++)
{
for (int j = i + 1; j < size; j++)
{
if (array[i] == array[j])
{
array[i - 1 ] = array[i]; /* WRONG! array[-1] = something */
size--;
}
}
}
If array[0] and array[1] are equal, array[0-1] = array[0], meaning that array[-1] = array[0]. You are not supposed to access array[-1].

Answer 2

I wouldn't make it even possible to create duplicates:
int main()
{
const int CAPACITY = 100;
cout << "Please enter a series of up to 100 integers. Press 'q' to quit. ";
std::set<int> myInts;
int input;
while (std::cin >> input && input != 'q' && myInts.size() <= CAPACITY) //note: 113 stops the loop, too!
myInts.insert(input);
std::cout << "Count: " << myInts.size();
}
And do yourself a favour and don't use raw arrays. Check out the STL.

Answer 3

#include <algorithm>
#include <iostream>
#include <iterator>
using namespace std;
int main()
{
vector<int> vec = {1,1,2,3,3,4,4,5,6,6};
auto it = vec.begin();
while(it != vec.end())
{
it = adjacent_find(vec.begin(),vec.end());
if(it != vec.end())
vec.erase(it);
continue;
}
for_each(vec.begin(),vec.end(),[](const int elem){cout << elem;});
return 0;
}
This code compiles with C++11.

Answer 4

#include<iostream>
#include<stdio.h>
using namespace std;
int arr[10];
int n;
void RemoveDuplicates(int arr[]);
void Print(int arr[]);
int main()
{
cout<<"enter size of an array"<<endl;
cin>>n;
cout<<"enter array elements:-"<<endl;
for(int i=0;i<n ;i++)
{
cin>>arr[i];
}
RemoveDuplicates(arr);
Print(arr);
}
void RemoveDuplicates(int arr[])
{
for(int i=0;i<n;i++)
{
for(int j=i+1;j<n;)
{
if(arr[i]==arr[j])
{
for(int k=j;k<n;k++)
{
arr[k]=arr[k+1];
}
n--;
}
else
j++;
}
}
}
void Print(int arr[])
{
for(int i=0;i<n;i++)
{
cout<<arr[i]<<" ";
}
}