Minimum number of swaps required to sort an array in C++

Problem statement

Given an array of N distinct elements, find the minimum number of swaps required to sort the array

Example

If array is {4, 2, 1, 3} then 2 swaps are required

• Swap arr[0] with arr[2]
• Swap arr[2] with arr[3}

Algorithm

1. Create a vector of pair in C++ with first element as array alues and second element as array indices.
2. Sort the vector of pair according to the first element of the pairs.
3. Traverse the vector and check if the index mapped with the value is correct or not, if not then keep swapping until the element is placed correctly and keep counting the number of swaps.

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
int getMinSwaps(int *arr, int n) {
   vector<pair<int, int>> vec(n);
   for (int i = 0; i < n; ++i) {
      vec[i].first = arr[i];
      vec[i].second = i;
   }
   sort(vec.begin(), vec.end());
   int cnt = 0;
   for (int i = 0; i < n; ++i) {
      if (vec[i].second == i) {
         continue;
      }
      swap(vec[i].first,vec[vec[i].second].first);
      swap(vec[i].second,vec[vec[i].second].second);
      if (i != vec[i].second) {
         --i;
      }
         ++cnt;
   }
   return cnt;
}
int main() {
   int arr[] = {4, 2, 1, 3};
   int n = sizeof(arr) / sizeof(arr[0]);
   cout << "Minimum swaps = " << getMinSwaps(arr, n) <<
   endl;
   return 0;
}

When you compile and execute above program. It generates following output

Output

Minimum swaps = 2

Narendra Kumar

Published on 23-Dec-2019 06:14:51

• Related Questions & Answers
• Program to find number of swaps required to sort the sequence in python
• Program to count number of minimum swaps required to make it palindrome in Python
• Minimum swaps required to make a binary string alternating in C++
• Minimum operations required to remove an array in C++
• Minimum Swaps required to group all 1’s together in C++
• Program to find out the number of shifts required to sort an array using insertion sort in python
• Program to find minimum swaps required to make given anagram in python
• Count minimum number of “move-to-front” moves to sort an array in C++
• Minimum number of operations required to delete all elements of the array using C++.
• Program to find expected number of shuffle required to sort the elements of an array in Python
• Minimum number of bottles required to fill K glasses in C++
• Minimum swaps required to bring all elements less than or equal to k together in C++
• Maximum and minimum of an array using minimum number of comparisons in C
• C++ Program to find out the minimum number of operations required to defeat an enemy
• Program to find how many swaps needed to sort an array in Python