How to Reverse an Array using STL in C++?

How to join two Arrays using STL in C++?

Last Updated : 07 Jul, 2022

Given two arrays, join these two arrays using STL in C++. Example:

Input: arr1[] = {1, 45, 54, 71, 76, 12}, arr2[] = {1, 7, 5, 4, 6, 12} Output: {1, 4, 5, 6, 7, 12, 45, 54, 71, 76} Input: arr1[] = {1, 7, 5, 4, 6, 12}, arr2[] = {10, 12, 11} Output: {1, 4, 5, 6, 7, 10, 11, 12}

Approach: Joining can be done with the help of set_union() function provided in STL. Syntax:

set_union (InputIterator1 first1, InputIterator1 last1,
           InputIterator2 first2, InputIterator2 last2,
           OutputIterator result);

Below is the implementation of the above approach:

CPP

// C++ program to join two Arrays 
// using set_union() in STL 
 
#include <bits/stdc++.h> 
using namespace std; 
 
int main() 
{ 
 
  // Get the array 
  int arr1[] = { 1, 45, 54, 71, 76, 12 }; 
  int arr2[] = { 1, 7, 5, 4, 6, 12 }; 
 
  // Compute the sizes 
  int n1 = sizeof(arr1) / sizeof(arr1[0]); 
  int n2 = sizeof(arr2) / sizeof(arr2[0]); 
 
  // Sort the arrays 
  sort(arr1, arr1 + n1); 
  sort(arr2, arr2 + n2); 
 
  // Print the array 
  cout << "First Array: "; 
  for (int i = 0; i < n1; i++) 
    cout << arr1[i] << " "; 
  cout << endl; 
 
  cout << "Second Array: "; 
  for (int i = 0; i < n2; i++) 
    cout << arr2[i] << " "; 
  cout << endl; 
 
  // Initialise a vector 
  // to store the merged values 
  // and an iterator 
  // to traverse this vector 
  vector<int> v(n1 + n2); 
  vector<int>::iterator it, st; 
 
  it = set_union(arr1, arr1 + n1, 
        arr2, arr2 + n2, 
        v.begin()); 
 
  // Print the merged array 
  cout << "\nAfter joining:\n"; 
  for (st = v.begin(); st != it; ++st) 
    cout << *st << ", "; 
  cout << '\n'; 
 
  return 0; 
} 

Output:

First Array: 1 12 45 54 71 76 
Second Array: 1 4 5 6 7 12 

After joining:
1, 4, 5, 6, 7, 12, 45, 54, 71, 76,

Time Complexity: O(nlogn)
Auxiliary Space: O(n)

How to Reverse an Array using STL in C++?

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