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Insertion sort using C++ STL

  • Difficulty Level : Hard
  • Last Updated : 30 Aug, 2017

Implementation of Insertion Sort using STL functions.

Pre-requisites : Insertion Sort, std::rotate, std::upper_bound, C++ Iterators.

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The idea is to use std::upper_bound to find an element making the array unsorted. Then we can rotate the unsorted part so that it ends up sorted. We can traverse the array doing these operations and the result will be a sorted array.

The code is offline on purpose to show hard-coded and easy to understand code.

// C++ program to implement insertion sort using STL.
#include <bits/stdc++.h>
// Function to sort the array
void insertionSort(std::vector<int> &vec)
    for (auto it = vec.begin(); it != vec.end(); it++)
        // Searching the upper bound, i.e., first 
        // element greater than *it from beginning
        auto const insertion_point = 
                std::upper_bound(vec.begin(), it, *it);
        // Shifting the unsorted part
        std::rotate(insertion_point, it, it+1);        
// Function to print the array
void print(std::vector<int> vec)
    for( int x : vec)
        std::cout << x << " ";
    std::cout << '\n';
// Driver code
int main()
    std::vector<int> arr = {2, 1, 5, 3, 7, 5, 4, 6};    


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