minimum swaps to sort an array
// C++ program to find minimum number of swaps
// required to sort an array
#include<bits/stdc++.h>
using namespace std;
// Function returns the minimum number of swaps
// required to sort the array
int minSwaps(int arr[], int n)
{
// Create an array of pairs where first
// element is array element and second element
// is position of first element
pair<int, int> arrPos[n];
for (int i = 0; i < n; i++)
{
arrPos[i].first = arr[i];
arrPos[i].second = i;
}
// Sort the array by array element values to
// get right position of every element as second
// element of pair.
sort(arrPos, arrPos + n);
// To keep track of visited elements. Initialize
// all elements as not visited or false.
vector<bool> vis(n, false);
// Initialize result
int ans = 0;
// Traverse array elements
for (int i = 0; i < n; i++)
{
// already swapped and corrected or
// already present at correct pos
if (vis[i] || arrPos[i].second == i)
continue;
// find out the number of node in
// this cycle and add in ans
int cycle_size = 0;
int j = i;
while (!vis[j])
{
vis[j] = 1;
// move to next node
j = arrPos[j].second;
cycle_size++;
}
// Update answer by adding current cycle.
if (cycle_size > 0)
{
ans += (cycle_size - 1);
}
}
// Return result
return ans;
}
// Driver program to test the above function
int main()
{
int arr[] = {1, 5, 4, 3, 2};
int n = (sizeof(arr) / sizeof(int));
cout << minSwaps(arr, n);
return 0;
}
# Python3 program to find the minimum
# number of swaps required to sort
# the given array
# Function to find minimum swaps
def minimumSwaps(arr):
# Initialise count variable
count = 0;
i = 0;
while (i < len(arr)):
# If current element is
# not at the right position
if (arr[i] != i + 1):
while (arr[i] != i + 1):
temp = 0;
# Swap current element
# with correct position
# of that element
temp = arr[arr[i] - 1];
arr[arr[i] - 1] = arr[i];
arr[i] = temp;
count += 1;
# Increment for next index
# when current element is at
# correct position
i += 1;
return count;
# Driver code
if __name__ == '__main__':
arr = [ 2, 3, 4, 1, 5 ];
# Function to find minimum swaps
print(minimumSwaps(arr));
# This code is contributed by 29AjayKumar
# Python3 program to find the minimum number
# of swaps required to sort an array
# of distinct element
# Function to find minimum swaps to
# sort an array
def findMinSwap(arr, n):
# Declare a vector of pair
vec = []
for i in range(n):
vec.append([arr[i], i])
# Sort the vector w.r.t the first
# element of pair
vec = sorted(vec)
ans, c, j = -1, 0, 0
for i in range(n):
# If the element is already placed
# correct, then continue
if(vec[i][1] == i):
continue
else:
# swap with its respective index
vec[i][0], vec[vec[i][1]][1] = \
vec[vec[i][1]][1], vec[i][0]
vec[i][1], vec[vec[i][1]][1] = \
vec[vec[i][1]][1], vec[i][1]
# swap until the correct
# index matches
if(i != vec[i][1]):
i -= 1
# each swap makes one element
# move to its correct index,
# so increment answer
ans += 1
return ans
# Driver code
arr = [1, 5, 4, 3, 2]
n = len(arr)
print(findMinSwap(arr,n))
# This code is contributed by mohit kumar 29
import java.io.*;
import java.math.*;
import java.util.*;
public class Swap {
static int minimumSwaps(int[] arr) {
int swap=0;
boolean visited[]=new boolean[arr.length];
for(int i=0;i<arr.length;i++){
int j=i,cycle=0;
while(!visited[j]){
visited[j]=true;
j=arr[j]-1;
cycle++;
}
if(cycle!=0)
swap+=cycle-1;
}
return swap;
}
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
int[] arr = new int[n];
for (int i = 0; i < n; i++) {
arr[i] = scanner.nextInt();
}
int res = minimumSwaps(arr);
System.out.println(res);
scanner.close();
}
}
// CPP program to find the minimum number
// of swaps required to sort an array
// of distinct element
#include<bits/stdc++.h>
using namespace std;
// Function to find minimum swaps to
// sort an array
int findMinSwap(int arr[] , int n)
{
// Declare a vector of pair
vector<pair<int,int>> vec(n);
for(int i=0;i<n;i++)
{
vec[i].first=arr[i];
vec[i].second=i;
}
// Sort the vector w.r.t the first
// element of pair
sort(vec.begin(),vec.end());
int ans=0,c=0,j;
for(int i=0;i<n;i++)
{
// If the element is already placed
// correct, then continue
if(vec[i].second==i)
continue;
else
{
// swap with its respective index
swap(vec[i].first,vec[vec[i].second].first);
swap(vec[i].second,vec[vec[i].second].second);
}
// swap until the correct
// index matches
if(i!=vec[i].second)
--i;
// each swap makes one element
// move to its correct index,
// so increment answer
ans++;
}
return ans;
}
// Driver code
int main()
{
int arr[] = {1, 5, 4, 3, 2};
int n = sizeof(arr)/sizeof(arr[0]);
cout<<findMinSwap(arr,n);
return 0;
}
