CODEWITHSUNDEEP
c++arrays
Huy Trần
Huy Trần

Reputation: 13

How can i remove the duplicate element in output / arrays?

#include <iostream>
using namespace std;

int main()
{
    const int ARRAY_SIZE = 10;
    int value[ARRAY_SIZE] = { 1, 2, 3, 4, 3, 4, 2, 3, 5, 6};
    int value2[100];
    for (int i = 0; i < ARRAY_SIZE; i++) 
    {
        for (int j = i + 1; j <= ARRAY_SIZE; j++)
        {
            if (value[i] == value[j]) 
            {
                cout << value[i] << " ";
            }
        }
    }
    return 0;
}

The output is

2 3 3 4 3

How can I make the output become 2 3 4 ?

Edit: I'm trying to print all numbers appearing more than once in the value array

I think I should create one more array to store value, but I stuck with it and don't know how to do it.

Upvotes: 0

Views: 83

Answers (2)

D&#250;thomhas
D&#250;thomhas

Reputation: 10048

It helps considerably to sort your array. Then you only need two indices:

  • a write index, starting at 0
  • a read index, starting at 1

Loop over your array using the read index. For every array[read] that has a duplicate value at array[read-1], IFF that value also does not exist at array[write], then copy it over and increment your write index.

Finally, the new length of your data is equal to your write index.

The basic idea is this: if I have a sorted list of values:

    1  3  3  4  5  5  5  7  7  9

Then I can easily see if a value is a duplicate or not by comparing the current (read) with the previous.

         ┌────┐
 1  3  3 │4  5│ 5  5  7  7  9   --  not duplicates
         └────┘
             ↑

            ┌────┐
 1  3  3  4 │5  5│ 5  7  7  9   --  duplicate values
            └────┘
                ↑

The only remaining trick is to make just a single copy of that value to the write index, which we can do by simply looking at the last thing we wrote.

Upvotes: 2

justANewb stands with Ukraine
justANewb stands with Ukraine

Reputation: 4663

You can use a std::map to count the number of times a value is in the array. If the number appears 2 or more times, then print it.

#include <iostream>
#include <map>

int main()
{
    const int ARRAY_SIZE = 10;
    int value[ARRAY_SIZE] = { 1, 2, 3, 4, 3, 4, 2, 3, 5, 6};
    std::map <int, int> mp;
    for(int i : value) 
        ++mp[i];
    for(const auto& p : mp) 
        if(p.second > 1)
            std::cout << p.first << ' ';
}

Link.

Upvotes: 1

Related Questions