Question

How to create a common sorted unique vector from 3 integer vectors in C++

Answer 1

#include <iostream>
#include <vector>
#include <set>

using std::vector;

/* 
   Function: mergeVectors
   Purpose:  Combine three integer vectors into a single vector.
*/
vector<int> mergeVectors(const vector<int>& a, const vector<int>& b, const vector<int>& c) {
    vector<int> merged;
    merged.insert(merged.end(), a.begin(), a.end());
    merged.insert(merged.end(), b.begin(), b.end());
    merged.insert(merged.end(), c.begin(), c.end());
    
    return merged;
}

/* 
   Function: uniqueSorted
   Purpose:  Convert a vector into a sorted list with unique elements.
             Uses std::set because it automatically sorts and removes duplicates.
*/
vector<int> uniqueSorted(const vector<int>& arr) {
    std::set<int> s(arr.begin(), arr.end());   // removes duplicates + sorts
    
    return vector<int>(s.begin(), s.end());
}

int main() {
    // Example input vectors
    vector<int> arr1 = {5, 1, 14, 3, 8, 9, 1, 1, 7};
    vector<int> arr2 = {3, 5, 7, 2, 3};
    vector<int> arr3 = {2, 9, 8};

    // Step 1: Merge all vectors
    vector<int> merged = mergeVectors(arr1, arr2, arr3);

    // Step 2: Create sorted unique list
    vector<int> result = uniqueSorted(merged);

    // Step 3: Print result
    std::cout << "Sorted unique vector: ";
    for (int x : result) {
        std::cout << x << " ";
    }
}



/* 
run:

Sorted unique vector: 1 2 3 5 7 8 9 14 

*/

 

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