NeetCode 1 word solutions

Question 1

W: Find Duplicate Elements in Array

Answer 1

Duplicates cannot be added in Hashmap.

Question 2

Find if two strings are anagram of each other

Answer 2

2 Hashmaps.

Add character as key and count as value.

Compare 2 Hashmaps.

Question 3

TWO SUM in an array

Answer 3

1 Hashmap.

Calculate difference = Target - n.

If Difference present in Map return. Else add it to hashmap.

Question 4

GROUP ANAGRAMS

Answer 4

o(m*n)

hashmap(list)

key = [list of same char/value count]

value = [list of strings]

Question 5

TOP K Frequent Elements

Answer 5

O(m+n)
Reverse bucket sort.

First count the nums using hashmap.

Array - index is count , value is array of numbers with that (index) count.

Read array from last index

Question 5

Encode and Decode String

Answer 5

1) Add number of characters followed by # before every string

2) Seperate each string with ; , If it already has ; , add \ esacpe character before every special character. to tell that consider the next character after \ as a part of string

3) JSON Serialisation 4) Hexadecimal;

Question 6

Product of Array except self without /

Answer 6

1) Using / is easy with O(n)

2) Prefix array * Postfix array - takes up space.

3) Single output array. Prefix variable and post fix variable.

Key is to fill the prefix/postfix variable value in the array position.

Question 7

Longest Sequence in An Array

Answer 7

Use the SET.
FInd if the value has previous element. If no then it is start of a sequence. Then find the next elements present or not.