Sort an array which contain 1 to n values

You have given an array which contain 1 to n element, your task is to sort this array in an efficient way and without replace with 1 to n numbers.

Examples:

Input : arr[] = {10, 7, 9, 2, 8, 
                 3, 5, 4, 6, 1};
Output : 1 2 3 4 5 6 7 8 9 10

Native approach :
Sort this array with the use of any type of sorting method. it takes O(nlogn) minimum time.

Efficient approach :
Replace every element with it’s position. it takes O(n) efficient time and give you the sorted array. Let’s understand this approach with the code below.

// Efficient C++ program to sort an array of
// numbers in range from 1 to n.
#include <iostream>
using namespace std;

// function for sort array
void sortit(int arr[], int n)
{
    for (int i = 0; i < n; i++) {

        // replace this element with it's position
        // while element not get the position
        // swap this element to it's position
        while (i != (arr[i] - 1)) 
            swap(arr[i], arr[arr[i] - 1]);        
    }
}

// Driver code
int main()
{
    int arr[] = { 10, 7, 9, 2, 8, 3, 5, 4, 6, 1 };
    int n = sizeof(arr) / sizeof(arr[0]);

    // for sort an array
    sortit(arr, n);

    // for print all the element in sorted way
    for (int i = 0; i < n; i++) 
        cout << arr[i] << " ";    
}

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DevanshuAgarwal

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