## Amazon Interview Question for Software Engineer / Developers

Country: United States
Interview Type: In-Person

Comment hidden because of low score. Click to expand.
1
of 1 vote

Lexicografically generated permutations O(n*n!)

``````boolean nextPerm(int [] nums)
{   int i =  nums.length - 2;
while(i >= 0) {
if(nums[i] < nums[i + 1])
break;
i--;
}
if (i ==  -1) {
return false;
}
int j =  nums.length - 1;
while(j > i) {
if(nums[j]>nums[i])
break;
j--;
}
if (j != i) {
swap(i,j,nums);
}
int k = i + 1;
int l = nums.length - 1;
while(k < l) {
swap(k,l,nums);
k++;
l--;
}
return true;

}
void swap(int i, int j, int[] arr) {
int temp = arr[j];
arr[j]=arr[i];
arr[i]=temp;
}
void generatePermutation(int[] nums) {
while (nextPerm(nums)) {
for (int i : nums)
System.out.print(i);
System.out.println();
}
}``````

Comment hidden because of low score. Click to expand.
0

the above solution is correct, as it finds the next permutation in linear time with constant space, but first you need to sort array in inceasing order to get the "lowest" value permutation. A heap sort is suitable since it O(1) memory.

Comment hidden because of low score. Click to expand.
0
of 0 vote

shall we generate all permutatitions of given list or only one permutation?

Comment hidden because of low score. Click to expand.
0

Sorry, I edited the question for clarity. All permutations

Comment hidden because of low score. Click to expand.
0
of 0 vote

I could reverse the list and this is one permutation, i don't get the point in this exercise.

Comment hidden because of low score. Click to expand.
0
of 0 vote

Java Implementation

3.import java.util.*;

4.import java.lang.*;

5.import java.io.*;

6.

7./* Name of the class has to be "Main" only if the class is public. */

8.class Ideone

9.{

10. public static void main (String[] args) throws java.lang.Exception

11. {

12. Integer[] input={1,2,3,4};

13. List<List<Integer>> ans=permute(input);

14. System.out.println(ans.size());

15. for (List<Integer> lstChild : ans){

16. System.out.println();

17.

18. for (Integer lstelement : lstChild)

19. System.out.print(lstelement);

20. }

21.

22. }

23.public static List<List<Integer>> permute(Integer...myInts){

24.

25. if(myInts.length==1){

26. List<Integer> arrayList = new ArrayList<Integer>();

28. List<List<Integer> > listOfList = new ArrayList<List<Integer>>();

30. return listOfList;

31. }

32.

33. Set<Integer> setOf = new HashSet<Integer>(Arrays.asList(myInts));

34.

35. List<List<Integer>> listOfLists = new ArrayList<List<Integer>>();

36.

37. for(Integer i: myInts){

38. ArrayList<Integer> arrayList = new ArrayList<Integer>();

40.

41. Set<Integer> setOfCopied = new HashSet<Integer>();

43. setOfCopied.remove(i);

44.

45. Integer[] isttt = new Integer[setOfCopied.size()];

46. setOfCopied.toArray(isttt);

47.

48. List<List<Integer>> permute = permute(isttt);

49. Iterator<List<Integer>> iterator = permute.iterator();

50. while (iterator.hasNext()) {

51. List<java.lang.Integer> list = iterator.next();

54.

55. }

56. }

57.

58.return listOfLists;

59. }

60.}

Comment hidden because of low score. Click to expand.
0
of 0 vote

``````3.import java.util.*;

4.import java.lang.*;

5.import java.io.*;

6.

7./* Name of the class has to be "Main" only if the class is public. */

8.class Ideone

9.{

10.	public static void main (String[] args) throws java.lang.Exception

11.	{

12.		Integer[] input={1,2,3,4};

13.		List<List<Integer>> ans=permute(input);

14.		System.out.println(ans.size());

15.		for (List<Integer> lstChild : ans){

16.			System.out.println();

17.

18.			for (Integer lstelement : lstChild)

19.			System.out.print(lstelement);

20.		}

21.

22.	}

23.public static List<List<Integer>> permute(Integer...myInts){

24.

25.        if(myInts.length==1){

26.            List<Integer> arrayList = new ArrayList<Integer>();

28.            List<List<Integer> > listOfList = new ArrayList<List<Integer>>();

30.            return listOfList;

31.        }

32.

33.        Set<Integer> setOf = new HashSet<Integer>(Arrays.asList(myInts));

34.

35.        List<List<Integer>> listOfLists = new ArrayList<List<Integer>>();

36.

37.        for(Integer i: myInts){

38.            ArrayList<Integer> arrayList = new ArrayList<Integer>();

40.

41.            Set<Integer> setOfCopied = new HashSet<Integer>();

43.            setOfCopied.remove(i);

44.

45.            Integer[] isttt = new Integer[setOfCopied.size()];

46.            setOfCopied.toArray(isttt);

47.

48.            List<List<Integer>> permute = permute(isttt);

49.            Iterator<List<Integer>> iterator = permute.iterator();

50.            while (iterator.hasNext()) {

51.                List<java.lang.Integer> list = iterator.next();

54.

55.            }

56.        }

57.

58.return listOfLists;

59.	}

60.}``````

Comment hidden because of low score. Click to expand.
0
of 0 vote

``````void printPerm(nums, s, p){
if( s == -1 || s == p) return;
if(p < nums.length) {
//swap
tmp = nums[p];
nums[p] = nums[p-1];
nums[p-1] = tmp;
}
for (num : nums) {
print num + " ";
}
print "\n"
printPerm(num, p, num.length -1);
p -= 1;
printPerm(num, s, p);

}

void main(...){
printPerm(nums, 0, nums.length)
}``````

Comment hidden because of low score. Click to expand.
0
of 0 vote

``````void printPerm(nums, s, p){
if( s == -1 || s == p) return;
if(p < nums.length) {
//swap
tmp = nums[p];
nums[p] = nums[p-1];
nums[p-1] = tmp;
}
for (num : nums) {
print num + " ";
}
print "\n"
printPerm(num, p, num.length -1);
p -= 1;
printPerm(num, s, p);

}

void main(...){
printPerm(nums, 0, nums.length)
}``````

Comment hidden because of low score. Click to expand.
0
of 0 vote

``````void printPerm(nums, s, p){
if( s == -1 || s == p) return;
if(p < nums.length) {
//swap
tmp = nums[p];
nums[p] = nums[p-1];
nums[p-1] = tmp;
}
for (num : nums) {
print num + " ";
}
print "\n"
printPerm(num, p, num.length -1);
p -= 1;
printPerm(num, s, p);

}

void main(...){
printPerm(nums, 0, nums.length)
}``````

Comment hidden because of low score. Click to expand.
0
of 0 vote

void printPerm(nums, s, p){
if( s == -1 || s == p) return;
if(p < nums.length) {
//swap
tmp = nums[p];
nums[p] = nums[p-1];
nums[p-1] = tmp;
}
for (num : nums) {
print num + " ";
}
print "\n"
printPerm(num, p, num.length -1);
p -= 1;
printPerm(num, s, p);

}

void main(...){
printPerm(nums, 0, nums.length)
}

Comment hidden because of low score. Click to expand.
0
of 0 vote

``````public void permutation(int[] array) {
int size = factorial(array.length);
for (int i = 0; i < size; i++) {
int i1 = i % array.length;
int i2 = (i + 1) % array.length;
int tmp = array[i1];
array[i1] = array[i2];
array[i2] = tmp;
printArray(array);
}}
public static int factorial(int value) {
if (value == 1) {
return 1;
}
return value * factorial(value - 1);``````

}

Comment hidden because of low score. Click to expand.
-1
of 1 vote

One random permutation?

``````private static void permutate(int arr[], int n) {
Random rand = new Random();
for(int i = n - 1; i > 0; --i) {
int j = rand.nextInt(i + 1);
int temp = arr[j];
arr[j] = arr[i];
arr[i] = temp;
}
}``````

Comment hidden because of low score. Click to expand.
0

Sorry, I edited the question for clarity. All permutations

Comment hidden because of low score. Click to expand.
-1
of 1 vote

One random permutation?

``````private static void permutate(int arr[], int n) {
Random rand = new Random();
for(int i = n - 1; i > 0; --i) {
int j = rand.nextInt(i + 1);
int temp = arr[j];
arr[j] = arr[i];
arr[i] = temp;
}``````

}

Comment hidden because of low score. Click to expand.
-1
of 1 vote

``````private static void permutate(int arr[], int n) {
Random rand = new Random();
for(int i = n - 1; i > 0; --i) {
int j = rand.nextInt(i + 1);
int temp = arr[j];
arr[j] = arr[i];
arr[i] = temp;
}``````

}

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