LPUSH and RPUSH for insertion in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the resulting list after LPUSH?

You start with an empty Redis list named 'fruits'. You run the command:
LPUSH fruits apple banana cherry
What is the order of elements in the list 'fruits' after this command?

Redis

LPUSH fruits apple banana cherry

A ["apple", "banana", "cherry"]

B ["cherry", "banana", "apple"]

C ["banana", "cherry", "apple"]

D ["apple", "cherry", "banana"]

💡 Hint

LPUSH inserts elements to the start of the list, from left to right.

LPUSH adds elements to the head of the list in the order they are given, so the last element ends up at the head.

❓ query_result

intermediate

What is the resulting list after RPUSH?

You have an empty Redis list named 'colors'. You run the command:
RPUSH colors red green blue
What is the order of elements in the list 'colors' after this command?

Redis

RPUSH colors red green blue

A ["blue", "green", "red"]

B ["red", "blue", "green"]

C ["green", "red", "blue"]

D ["red", "green", "blue"]

💡 Hint

RPUSH adds elements to the end of the list in the order they appear.

RPUSH appends elements to the tail of the list in the order given, so the list keeps the same order as the arguments.

📝 Syntax

advanced

Which LPUSH command is syntactically correct?

Which of the following LPUSH commands will run without syntax errors in Redis?

A LPUSH mylist "one" "two" "three"

B LPUSH mylist (one, two, three)

C LPUSH mylist [one two three]

D LPUSH mylist one; two; three

💡 Hint

Redis commands take arguments separated by spaces, no brackets or commas.

Only option A uses the correct Redis command syntax with space-separated arguments and optional quotes for strings.

❓ query_result

advanced

What is the list after mixed LPUSH and RPUSH?

You start with an empty Redis list named 'numbers'. You run these commands in order:
1. RPUSH numbers 1 2 3
2. LPUSH numbers 0
3. RPUSH numbers 4
What is the final order of elements in the list 'numbers'?

Redis

RPUSH numbers 1 2 3
LPUSH numbers 0
RPUSH numbers 4

A [0, 4, 1, 2, 3]

B [1, 2, 3, 0, 4]

C [0, 1, 2, 3, 4]

D [4, 3, 2, 1, 0]

💡 Hint

LPUSH adds to the front, RPUSH adds to the end.

RPUSH adds 1,2,3 to the end, LPUSH adds 0 to the front, then RPUSH adds 4 to the end, resulting in [0,1,2,3,4].

🧠 Conceptual

expert

Why choose LPUSH over RPUSH in Redis list insertion?

Which reason best explains when LPUSH is preferred over RPUSH for inserting elements into a Redis list?

A When you want to add elements to the start of the list quickly, like a stack (LIFO) behavior.

B When you want to add elements to the end of the list to maintain insertion order (FIFO).

C When you want to sort the list automatically after insertion.

D When you want to remove elements from the list instead of adding.

💡 Hint

LPUSH adds elements at the head, useful for last-in-first-out order.

LPUSH inserts at the front, making it ideal for stack-like behavior where the last added element is first to be removed.