ZRANGE and ZREVRANGE for reading in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this ZRANGE command?

Given a sorted set myzset with elements {"one":1, "two":2, "three":3, "four":4}, what does the command ZRANGE myzset 1 2 return?

Redis

ZRANGE myzset 1 2

A ["four", "three"]

B ["three", "four"]

C ["two", "three"]

D ["one", "two"]

💡 Hint

ZRANGE returns elements by rank starting at 0, inclusive.

ZRANGE returns elements by their rank in ascending order. Index 1 is "two", index 2 is "three".

❓ query_result

intermediate

What is the output of this ZREVRANGE command?

Given a sorted set myzset with elements {"one":1, "two":2, "three":3, "four":4}, what does the command ZREVRANGE myzset 0 1 return?

Redis

ZREVRANGE myzset 0 1

A ["four", "three"]

B ["one", "two"]

C ["three", "two"]

D ["two", "one"]

💡 Hint

ZREVRANGE returns elements by rank in descending order starting at 0.

ZREVRANGE returns elements starting from the highest score. Index 0 is "four", index 1 is "three".

📝 Syntax

advanced

Which command correctly returns elements with scores included?

You want to get elements and their scores from myzset using ZRANGE. Which command is correct?

A ZRANGE myzset 0 -1 WITHSCORE

B ZRANGE myzset 0 -1 WITHSCORES

C ZRANGE myzset 0 -1 WITH SCORES

D ZRANGE myzset 0 -1 SCORES

💡 Hint

The option to include scores is a single word.

The correct syntax is WITHSCORES as one word without spaces.

❓ optimization

advanced

How to efficiently get the top 3 highest scored elements with scores?

Which command is the most efficient to get the top 3 elements with highest scores and their scores from myzset?

A ZREVRANGE myzset 0 2 WITHSCORES

B ZRANGE myzset -3 -1 WITHSCORES

C ZRANGE myzset 0 2 WITHSCORES

D ZREVRANGE myzset -3 -1 WITHSCORES

💡 Hint

Top highest means descending order starting at 0.

ZREVRANGE with 0 2 returns top 3 elements in descending order efficiently.

🧠 Conceptual

expert

What happens if you use negative indexes in ZRANGE?

Given myzset with 5 elements, what does ZRANGE myzset -3 -1 return?

Redis

ZRANGE myzset -3 -1

A Returns an empty list

B Returns the first 3 elements in ascending order

C Raises a syntax error

D Returns the last 3 elements in ascending order

💡 Hint

Negative indexes count from the end backwards.

Negative indexes in ZRANGE count from the end, so -3 to -1 returns last 3 elements in ascending order.