Remove Duplicates from Sorted Array in C++

To remove duplicates from a sorted array in C++, you can implement a simple algorithm that iterates through the array and eliminates any duplicate elements in-place. Here’s an example of how to do this:

#include <iostream>
#include <vector>

// Function to remove duplicates from a sorted array
int removeDuplicates(std::vector<int>& nums) {
    if (nums.empty()) {
        return 0; // Return 0 for an empty array
    }

    int uniqueCount = 1; // Initialize the count of unique elements to 1

    for (int i = 1; i < nums.size(); ++i) {
        // If the current element is different from the previous one, update it
        if (nums[i] != nums[i - 1]) {
            nums[uniqueCount] = nums[i];
            ++uniqueCount;
        }
    }

    return uniqueCount; // Return the count of unique elements
}

int main() {
    std::vector<int> nums = {1, 1, 2, 2, 2, 3, 4, 4, 5, 5, 5};

    int uniqueCount = removeDuplicates(nums);

    std::cout << "Unique Count: " << uniqueCount << std::endl;
    std::cout << "Unique Array: ";
    for (int i = 0; i < uniqueCount; ++i) {
        std::cout << nums[i] << " ";
    }
    std::cout << std::endl;

    return 0;
}

In this example:

• We define a removeDuplicates function that takes a reference to a std::vector<int> as its parameter.
• The function iterates through the sorted array and keeps track of a uniqueCount variable, which represents the count of unique elements encountered so far.
• If the current element is different from the previous one, it is considered a unique element, and we update the array at the position uniqueCount with the current element.
• After processing the entire array, the function returns the value of uniqueCount, representing the count of unique elements.
• In the main function, we call removeDuplicates on a sorted vector of integers and print the count of unique elements as well as the unique elements themselves.

The result of running this program will be:

Unique Count: 5
Unique Array: 1 2 3 4 5 

The duplicate elements have been removed from the sorted array, and the unique elements are left in the array with the appropriate count.