Leetcode

Question 1

Find duplicate number

Answer 1

use slow and fast pointer and where both meet is circular detection and that is duplicate number

Question 2

search 2D

Answer 2

if it is sorted, then increment row or column based on the range. Like binary search

Question 3

Find duplicates in two lists

Answer 3

use set and keep putting into set

Question 4

Find the first and last position of element in sorted array

Answer 4

Use binary search and then keep incrementing and decrementing on that position

Question 5

Merge sort

Answer 5

see which is one small and keep moving until 2one is bigger

Question 6

Color sorting

Answer 6

as the range is small, use bucket or counter index, or use set to increment

Question 7

Relative sort array

Answer 7

2N: FOR array 1 -> check exists in array 2 and put in dictionary with counter. Then run FOR loop on array 2 to print in that order

Question 8

K-frequent numbers

Answer 8

First use bucket sort and then use frequnecy with MaxHeap and pop 3 times