Coding Interview Questions

Question 1

Copy char[] to String

1. char[].toString()
2. new String(char[])
3. String.valueOf(char[])

Answer 1

2. new String(char[])

3. String.valueOf(char[])

Question 2

Which one of the two is correct?

1. int[] sequence = new int[]{0, 1};
2. int[] sequence = {0, 1};

Answer 2

Both 1 and 2 are correct.

1. int[] sequence = new int[]{0, 1};
2. int[] sequence = {0, 1};

Question 3

Initialize a List with values:

1. ArrayList list = new ArrayList(); list.add(item1);
2. ArrayList list = new ArrayList() { item1 };

Answer 3

1. ArrayList list = new ArrayList();
   list.add(item1);

Question 4

public class Test {
class A { }
static class B { }
public static void main(String[] args) {
A a = new A();
B b = new B();
}
}
1. A instantiation will compile, no instance of Test is needed to instantiate A
2. B instantiation will compile, no instance of Test is needed to instantiate B
3. B will fail, you need an instance of Test to instantiate B
4. A will fail, you need an instance of Test to instantiate A

Answer 4

2. B instantiation will compile, no instance of Test is needed to instantiate B
3. A will fail, you need an instance of Test to instantiate A

Question 5

Get List size given List list;

1. list.length;
2. list.size();

Answer 5

2. list.size()

Question 6

Initialize a List:

1. List nodes = new ArrayList<>();
2. List nodes = new List<>();

Answer 6

1. List nodes = new ArrayList<>();

Question 7

Which one is correct?

1. O(nlog(n))
2. O(n log n)

Answer 7

1. O(nlog(n))

Question 8

How to sort an ArrayList?

1. arrayList.sort()
2. Collections.sort(arrayLIst);

Answer 8

2. Collections.sort(arrayLIst);

Question 9

Get character counts from map Map

1. map.merge(chr, 1, Integer::sum);
2. map.put(chr, map.getOrDefault(chr, 0) + 1);

Answer 9

Both 1 and 2 are correct

Question 10

Traverse Character type chars in string

1. for (int i = 0; i < s.length(); i++) { s.charAt(i); }
2. s.chars().forEach(chr -> { })
3. for (Character chr : s) { }

Answer 10

1. for (int i = 0; i < s.length(); i++) { s.charAt(i); }

Question 11

Add key value to map

1. map[key] = value;
2. map.put(key, value);

Answer 11

2. map.put(key, value);

Question 12

The ‘a’ char code is

1. 79
2. 97
3. 48
4. 84

Answer 12

2. 97

Question 13

The ‘0’ (zero) char code is

1. 48
2. 84
3. 56
4. 65

Answer 13

1. 48

Question 14

The ‘A’ char code is

1. 97
2. 79
3. 65
4. 56

Answer 14

3. 65

Question 15

The best conceivable runtime means

1. it is the best time you can conceive that the problem could possibly be solved in, and it is definitely impossible for the problem to be solved faster than that.
2. you have an algorithm that solves the problem, and in the best case, that algorithm has a particular time complexity.
3. you are feeding the worst possible input (of that size) into your algorithm

Answer 15

1. it is the best time you can conceive that the problem could possibly be solved in, and it is definitely impossible for the problem to be solved faster than that.

Question 16

String input = …;

1. char chr = Input.charCodeAt(4);
2. int chr = Input.charCodeAt(4);
3. char chr = input.charAt(4);
4. int chr = input.charAt(4);

Answer 16

3. char chr = input.charAt(4);

Question 17

Select valid statements

1. Int codePoint = fifthCharl
2. int codePoint = (int) fifthChar
3. char opp = (char);
4. int opp = (char);

Answer 17

2. int codePoint = (int) fifthChar

3. char opp = (char);

Question 18

Are the following expressions valid? (Yes/No)

1. ‘z’ - ‘a’
2. ‘a’ + int

Answer 18

Yes

Question 19

Why is the following valid?
char c = 'a' + 10;
But, not the following?
int i = 10;
char c = 'a' + i;

Answer 19

Because the compiler can check that it (‘a’ + 10) is within the bounds of a char whereas it cannot (in general) check that ‘a’ + is within the bounds.

Question 20

What is the result of evaluating the following?
26 % 26

1. 26
2. 0
3. 1

Answer 20

2. 0

Question 21

What is the result of evaluating the following?
27 % 26
1. 26
2. 0
3. 1

Answer 21

3. 1

Question 22

What is the result of evaluating the following?
25 % 26
1. 25
2. 0
3. 1

Answer 22

1. 25

Question 23

1. array.length;

2. array.length();

Answer 23

1. array.length;

Question 24

Math.floor returns

1. integer
2. double
3. float

Answer 24

2. double

Question 25

1. MIN_VAL
2. Integer.MIN_VALUE
3. Integer.MIN_VAL

Answer 25

2. Integer.MIN_VALUE

Question 26

1. new Map<>{};
2. new Map<>();
3. new HashMap<>{};
4. new HashMap<>();

Answer 26

4. new HashMap<>();

Question 27

1. map.contains(key);
2. map.has(key);
3. map.containsKey(key);

Answer 27

3. map.containsKey(key);

Question 28

1. static method cannot be referenced from a static context
2. non-static method cannot be referenced from a non-static context
3. non-static method cannot be referenced from a static context
4. static method cannot be referenced from a non-static context

Answer 28

3. non-static method cannot be referenced from a static context

Question 29

In a graph

1. vertices are the nodes and edges are the connections
2. vertices are the connections and edges are the nodes

Answer 29

1. vertices are the nodes and edges are the connections

Question 30

1. Trees are graphs that contain cycles.

2. Trees are graphs that do not contain even a single cycle.

Answer 30

2. Trees are graphs that do not contain even a single cycle.

Question 31

In a graph, acyclic refers to:

1. contains no cycles
2. contains cycles

Answer 31

1. contains no cycles

Question 32

DFS time complexity in a tree is:

1. O(V + E)
2. O(V)
3. O(V^2)

Answer 32

2. O(V)

Question 33

DFS time complexity in a graph is;

1. O(V + E)
2. O(V)
3. O(V^2)

Answer 33

1. O(V + E)

Question 34

List is interchangeable with ArrayList?

1. True
2. False

Answer 34

2. False

Question 35

Object element

1. element instanceof ArrayList
2. element typeof ArrayList

Answer 35

1. element instanceof ArrayList

Question 36

Cast Object to List given: Object obj;

1. Arrays.asList(obj)
2. (List) obj

Answer 36

2. (List) obj

Question 37

Which one is considered better?

1. List myList = new ArrayList();
2. ArrayList myList = new ArrayList();

Answer 37

1. List myList = new ArrayList();

Question 38

Which one is correct to transform a resizable list of chars into a String?
  1. List chars = new ArrayList<>();
  chars.add(chr);
  return new String(chars);
  2. StringBuilder chars = new StringBuilder();
  chars.append(chr)
  return chars.toString();

Answer 38

2. StringBuilder chars = new StringBuilder();
   chars.append(chr)
   return chars.toString();