How to prepare for a coding round on HackerRank / HackerEarth

Practise on the real test screen
HackerRank's practice page uses the same editor, stdin/stdout rules and hidden test cases as company tests. Start with the Interview Preparation Kit and solve Easy and Medium problems in the language you will use on test day.
```
hackerrank.com/interview/preparation-kit
```
Learn the input format first
Test input comes from stdin and you must print only the answer to stdout. Don't print prompts like "Enter n". Memorise the input-reading snippet for your language.
```
Python:
n = int(input())
a = list(map(int, input().split()))
```
Check constraints before you code
Constraints tell you which approach passes. A 1-2 second limit allows roughly 10^8 simple operations. If brute force is O(n²) and n is 10^5, you will time out on hidden cases. Think hash maps, sorting, two pointers or prefix sums.
```
n ≤ 1000 → O(n²) is fine
n ≤ 10^5 → aim for O(n log n)
n ≤ 10^6 → aim for O(n)
```
Test edge cases yourself
Sample cases usually pass; hidden cases break you. Use Run Code with custom input before you submit and try the cases below.
```
n = 1
all elements equal
already sorted / reverse sorted
negative numbers and zero
maximum n (check speed)
empty or single character string
```
Know the company and the pattern
Each company's coding round differs in number of questions, time limit, negative marking and partial scoring. Read the invite email fully and check how the company hires on Hirastra. Then open today's verified openings and apply while they are fresh.
```
hirastra.com/companies
```

Skip the searching: today's verified openings are posted three times a day with official apply links, and you can check your resume against any of them with the free ATS checker.

Practise on the real test screen

Learn the input format first

Check constraints before you code

Test edge cases yourself

Know the company and the pattern