PhonePe interview prep

DSAMedium

What is the time complexity of inserting one element into a binary heap of n elements?

1. O(n log n)
2. O(1)
3. O(n)
4. O(log n)

This topic is named in a candidate’s interview report: SDE (Android) interview, 2025, on Reddit.

DSAEasy

Which data structure is the natural fit for checking whether brackets like ([]{}) are balanced?

1. A stack
2. A queue
3. A hash set
4. A binary search tree

This topic is named in a candidate’s interview report: On-campus interview, 2023, on GeeksforGeeks.

DSAMedium

A spell checker must say whether a word is in its dictionary and list the dictionary words that start with what was typed. Which data structure suits this best?

1. A trie (prefix tree)
2. A stack
3. A min-heap
4. A queue

This topic is named in a candidate’s interview report: On-campus interview, 2023, on GeeksforGeeks.

DSAMedium

Each element of [2, 3, 1, 1, 4] is the longest jump you can make from that position. What is the fewest jumps needed to reach the last index from index 0?

1. 3
2. 1
3. 4
4. 2

This topic is named in a candidate’s interview report: SDE (Android) interview, 2025, on Reddit.

DSAMedium

Dots are put into the digit string "25525511135" to make valid IPv4 addresses: four parts, each 0 to 255, with no leading zeros. How many valid addresses are there?

1. 1
2. 3
3. 2
4. 4

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

DSAEasy

The sorted array [1, 1, 2, 3, 3, 3, 4] must have its duplicates removed in place, returning how many unique values it now keeps at the front. What does the two-pointer method return, and at what cost?

1. 4, in O(n log n) time and O(1) extra space
2. 7, in O(n) time and O(n) extra space
3. 4, in O(n) time and O(1) extra space
4. 4, in O(n) time and O(n) extra space

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

PythonMedium

What does this print?

def follows(pattern, s):
    words = s.split()
    if len(words) != len(pattern):
        return False
    return len(set(pattern)) == len(set(words)) == len(set(zip(pattern, words)))

print(follows("abba", "dog cat cat dog"), follows("abba", "dog dog dog dog"))

1. True True
2. True False
3. False True
4. False False

This topic is named in a candidate’s interview report: SDE (Android) interview, 2025, on Reddit.

OOPMedium

What is the difference between static (early) and dynamic (late) binding?

1. Static binding picks the method when the program is compiled, as for overloads; dynamic binding picks the override at run time from the object's real type
2. Dynamic binding happens at compile time
3. They are the same thing
4. Static binding only applies to variables

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

OOPMedium

Which lazily created Java singleton is thread-safe without taking a lock on every call?

1. if (inst == null) inst = new Logger(); return inst; inside a static get()
2. A public constructor that callers agree to call only once
3. A holder class: private static class Holder { static final Logger I = new Logger(); } and get() returns Holder.I
4. A static field that every constructor call overwrites

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

OOPEasy

How does abstraction differ from encapsulation?

1. They are two names for the same idea
2. Abstraction needs inheritance and encapsulation needs interfaces
3. Abstraction shows what an object does and hides how; encapsulation keeps an object's data together with its methods and stops outside code from changing the data directly
4. Encapsulation hides whole classes from other packages, nothing more

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

DBMS and SQLMedium

scores holds 95, 90, 90, 85 and 80. What does this return?

SELECT score FROM scores
ORDER BY score DESC
LIMIT 1 OFFSET 2;

1. 85
2. 90
3. 80
4. 95

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

Operating systemsEasy

Which Linux command lists the running processes with their process IDs?

1. ls -l
2. df -h
3. ps aux
4. cat /etc/passwd

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

Operating systemsMedium

After chmod 754 report.sh, what may members of the file's group do with it?

1. Read, change and run it
2. Only read it
3. Nothing
4. Read it and run it, but not change it

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

Operating systemsEasy

A line of app.log contains "error" twice and another line contains it once. What does grep -c error app.log print?

1. 3
2. 2
3. Both matching lines
4. The line numbers of the matches

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

Computer networksMedium

How do the layers of the TCP/IP model line up with the OSI model?

1. TCP/IP has the same seven layers
2. TCP/IP's application layer covers OSI application, presentation and session; transport and internet match OSI transport and network; the link layer covers data link and physical
3. TCP/IP has no transport layer
4. OSI is what the internet runs on; TCP/IP is only a teaching model

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

Computer networksEasy

An API answers with a status code in the 4xx range. What does that tell the caller?

1. The request worked
2. The server broke while handling a valid request
3. The resource has moved
4. The request itself cannot be served as sent: it is malformed, lacks a login, is not allowed or names something that does not exist

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

Computer networksMedium

A browser sends If-None-Match with the ETag of its cached copy, and the page has not changed. What should the server answer?

1. 200 OK with the whole page again
2. 304 Not Modified, with no body, so the browser uses its cached copy
3. 204 No Content
4. 412 Precondition Failed

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.

AptitudeMedium

With a 3-litre and a 5-litre jug: fill the 5 and pour into the 3 until it is full, empty the 3, pour the 5's remainder into the 3, then fill the 5 again and top up the 3. How much is left in the 5-litre jug?

1. 3 litres
2. 2 litres
3. 4 litres
4. 1 litre

This topic is named in a candidate’s interview report: On-campus interview, 2024, on GeeksforGeeks.