Problems

Question 1

Describe how you would combine two arrays where n is the length or the old array so that

result[i] == input[i]
result[i+n]==input[i]

And what is the time complexity?

Answer 1

1. Create an ans array with space twice the size of the input array
2. loop through the the length of the input array
   2.1 And each time set
   result[i] = result[i+1] = input[i]

Question 2

What does Bitwise XOR do and how do you write it in Java?

Answer 2

Copies the bit if it is set in one operand but not both.

^ is the operator used for XOR in Java

Question 3

How could you return the indices of 2 elements that add up to the sum?

Answer 3

1. Create a HashMap
2. compl = target - current
3. check if compl is in map, if it is return the indices
4. if compl not in map, add it to map

Question 4

How could you check if a list contains duplicates?

Answer 4

1. Create a HashSet
2. If set contains current value, return true
3. If set doesn’t have current value, add to set
4. If we never find duplicates, return false