https://www.hackerrank.com/challenges/minimum-swaps-2/problem
Minimum Swaps II
You are given an unordered array consisting of consecutive integers [1, 2, 3, ..., n] without any duplicates. You are allowed to swap any two elements. You need to find the minimum number of swaps required to sort the array in ascending order.
For example, given the array we perform the following steps:
i arr swap (indices)
0 [7, 1, 3, 2, 4, 5, 6] swap (0,3)
1 [2, 1, 3, 7, 4, 5, 6] swap (0,1)
2 [1, 2, 3, 7, 4, 5, 6] swap (3,4)
3 [1, 2, 3, 4, 7, 5, 6] swap (4,5)
4 [1, 2, 3, 4, 5, 7, 6] swap (5,6)
5 [1, 2, 3, 4, 5, 6, 7]
It took swaps to sort the array.
Function Description
Complete the function minimumSwaps in the editor below. It must return an integer representing the minimum number of swaps to sort the array.
minimumSwaps has the following parameter(s):
- arr: an unordered array of integers
Input Format
The first line contains an integer, , the size of .
The second line contains space-separated integers .
Constraints
Output Format
Return the minimum number of swaps to sort the given array.
Sample Input 0
4 4 3 1 2
Sample Output 0
3
Explanation 0
Given array
After swapping we get
After swapping we get
After swapping we get
So, we need a minimum of swaps to sort the array in ascending order.
Sample Input 1
5 2 3 4 1 5
Sample Output 1
3
Explanation 1
Given array
After swapping we get
After swapping we get
After swapping we get
So, we need a minimum of swaps to sort the array in ascending order.
Sample Input 2
7 1 3 5 2 4 6 8
Sample Output 2
3
Explanation 2
Given array
After swapping we get
After swapping we get
After swapping we get
So, we need a minimum of swaps to sort the array in ascending order.
https://www.geeksforgeeks.org/minimum-number-swaps-required-sort-array/
Given an array of n distinct elements, find the minimum number of swaps required to sort the array.
Examples:
Input : {4, 3, 2, 1}
Output : 2
Explanation : Swap index 0 with 3 and 1 with 2 to
form the sorted array {1, 2, 3, 4}.
Input : {1, 5, 4, 3, 2}
Output : 2
// Java program to find minimum number of swaps
// required to sort an array
import javafx.util.Pair;
import java.util.ArrayList;
import java.util.*;
class GfG
{
// Function returns the minimum number of swaps
// required to sort the array
public static int minSwaps(int[] arr)
{
int n = arr.length;
// Create two arrays and use as pairs where first
// array is element and second array
// is position of first element
ArrayList <Pair <Integer, Integer> > arrpos =
new ArrayList <Pair <Integer, Integer> > ();
for (int i = 0; i < n; i++)
arrpos.add(new Pair <Integer, Integer> (arr[i], i));
// Sort the array by array element values to
// get right position of every element as the
// elements of second array.
arrpos.sort(new Comparator<Pair<Integer, Integer>>()
{
@Override
public int compare(Pair<Integer, Integer> o1,
Pair<Integer, Integer> o2)
{
if (o1.getKey() > o2.getKey())
return -1;
// We can change this to make it then look at the
// words alphabetical order
else if (o1.getKey().equals(o2.getKey()))
return 0;
else
return 1;
}
});
// To keep track of visited elements. Initialize
// all elements as not visited or false.
Boolean[] vis = new Boolean[n];
Arrays.fill(vis, 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.get(i).getValue() == 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] = true;
// move to next node
j = arrpos.get(j).getValue();
cycle_size++;
}
// Update answer by adding current cycle.
ans += (cycle_size - 1);
}
// Return result
return ans;
}
}
// Driver class
class MinSwaps
{
// Driver program to test the above function
public static void main(String[] args)
{
int []a = {1, 5, 4, 3, 2};
GfG g = new GfG();
System.out.println(g.minSwaps(a));
}
}
// This code is contributed by Saksham Seth
原文地址：https://www.cnblogs.com/lightwindy/p/9650776.html