CRED Coding Questions

Overview

Practice CRED coding questions in the style candidates report for online assessments and technical interviews. Focus: hashing, streams, intervals, correctness under retries.

CRED coding pattern

Item	Typical expectation
Problems	1-3 coding tasks depending on drive
Skills	hashing, streams, intervals, correctness under retries
Languages	Java, C++, Python (confirm invite)
Bar	Correctness first, then complexity

Practice problems

Question 1: design hit counter (last 5 minutes)

Show approach

Approach: Bucketed timestamps.

Map<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
  // fill logic
}

Complexity: State time/space before coding. Test empty input and single-element cases.

Question 2: detect duplicate transaction ids in window w

Show approach

Approach: Queue + set eviction.

from collections import defaultdict
def solve(arr):
  # fill logic
  return arr

Complexity: State time/space before coding. Test empty input and single-element cases.

Question 3: first unique transaction in a stream

Show approach

Approach: Queue + frequency map.

Map<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
  // fill logic
}

Complexity: State time/space before coding. Test empty input and single-element cases.

Question 4: minimum transfers to settle balances

Show approach

Approach: Backtracking on non-zero balances.

from collections import defaultdict
def solve(arr):
  # fill logic
  return arr

Complexity: State time/space before coding. Test empty input and single-element cases.

Question 5: sliding window maximum

Show approach

Approach: Deque of indices.

Map<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
  // fill logic
}

Complexity: State time/space before coding. Test empty input and single-element cases.

Question 6: validate rate limit n calls / t seconds

Show approach

Approach: Timestamp queue.

from collections import defaultdict
def solve(arr):
  # fill logic
  return arr

Complexity: State time/space before coding. Test empty input and single-element cases.

Question 7: subarray sum equals k

Show approach

Approach: Prefix sum hash map.

Map<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
  // fill logic
}

Complexity: State time/space before coding. Test empty input and single-element cases.

Pattern drill plan (2 weeks)

Day	Drill
Mon	Arrays + hashing (2 problems)
Tue	Two pointers / sliding window
Wed	Stacks / strings
Thu	Trees or graphs basics
Fri	Timed mock (2 problems / 90 min)
Sat	Re-solve Friday misses cold
Sun	Light CS theory + rest

Common coding mistakes

Coding before reading constraints
Passing samples but failing hidden tests
Silent complexity (cannot explain Big-O in interview)
Switching languages mid-prep
Never practicing on the real OA editor style

Comments & Suggestions

Preparation guide

Aptitude / mock quiz

Interview experience

CRED hub

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