Leaderboard implementation in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a user with a score to the leaderboard.

Redis

ZADD leaderboard [1] user123

Drag options to blanks, or click blank then click option'

A1500

Bleaderboard

CZADD

DSCORE

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the member name before the score

Using a string instead of a number for the score

The ZADD command requires the score before the member name. Here, 1500 is the score for user123.

2fill in blank

medium

Complete the code to get the top 3 users from the leaderboard.

Redis

ZREVRANGE leaderboard 0 [1] WITHSCORES

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A2

B3

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 3 as the end index which returns 4 users

Using 1 as the end index which returns only 2 users

The ZREVRANGE command uses zero-based indexes. To get the top 3 users, use 0 to 2.

3fill in blank

hard

Fix the error in the code to increment a user's score by 50.

Redis

ZINCRBY leaderboard [1] user123

Drag options to blanks, or click blank then click option'

AINCR

Bleaderboard

CZINCRBY

D50

Attempts:

3 left

💡 Hint

Common Mistakes

Using the command name as an argument

Putting the member name before the increment

The ZINCRBY command syntax is ZINCRBY key increment member. The increment value 50 must be the second argument.

4fill in blank

hard

Fill both blanks to remove a user from the leaderboard and then check if the user still exists.

Redis

ZREM leaderboard [1]
ZSCORE leaderboard [2]

Drag options to blanks, or click blank then click option'

Auser123

Buser456

Duser789

Attempts:

3 left

💡 Hint

Common Mistakes

Using different user names in the two commands

Using a user name that was never added

ZREM removes the member user123 from the leaderboard. Then ZSCORE checks the score of user123 to confirm removal.

5fill in blank

hard

Fill all three blanks to create a leaderboard, add two users, and get the rank of one user.

Redis

ZADD [1] 1000 [2] 1500 [3]
ZRANK [1] [2]

Drag options to blanks, or click blank then click option'

Aleaderboard

BuserA

CuserB

DuserC

Attempts:

3 left

💡 Hint

Common Mistakes

Using different leaderboard names in commands

Mixing up user names in add and rank commands

The leaderboard is named leaderboard. We add userA with score 1000 and userB with 1500. Then we get the rank of userA in the leaderboard.