-
Notifications
You must be signed in to change notification settings - Fork 0
/
Permutations.java
50 lines (47 loc) · 1.56 KB
/
Permutations.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
import java.util.*;
public class Permutations
{
private void computePermutations(List<Integer> al,int[] arr,int[] hash,int n,List<List<Integer>> sol)
{
//Base Case
if(al.size()==n)
{
sol.add(new ArrayList<>(al));
return;
}
for(int i=0;i<n;i++)
{
if(hash[i]!=1)
{
al.add(arr[i]);
hash[i]=1;
computePermutations(al,arr,hash,n,sol);
//Backtrack -> Removes element from last index in array list and sets hash value to 0
al.remove(al.size()-1);
hash[i]=0;
}
}
}
private List<List<Integer>> permute(int[] nums) {
int n = nums.length;
int[] hash = new int[n];
//Array consisting of 0s and 1s. If 0, element has not been picked,
//Else element has been picked
Arrays.fill(hash,0);
List<List<Integer>> ans = new ArrayList<>();
computePermutations(new ArrayList<>(),nums,hash,n,ans);
return ans;
}
public static void main(String[] args) {
int[] nums = {1,5,7,9};
List<List<Integer>> listOfPermutations = new ArrayList<List<Integer>>();
Permutations obj = new Permutations();
listOfPermutations = obj.permute(nums);
System.out.print("[ ");
for(List<Integer> itr:listOfPermutations)
{
System.out.print(itr.toString()+" ");
}
System.out.println("]");
}
}