Solution: Map Sum Pairs
Explore how to implement a MapSum class using a trie to support inserting string keys with integer values and calculating the sum of all values corresponding to keys beginning with a given prefix. Understand how to handle updates efficiently by maintaining cumulative prefix sums and using a hash map to track current key values. This lesson covers time and space complexities and shows how tries optimize prefix-based queries.
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Statement
Design a data structure that supports the following operations:
Insert a key-value pair:
Each key is a string, and each value is an integer.
If the key already exists, update its value to (overriding the previous value).
Return the prefix sum:
Given a string,
prefix, return the total sum of all values associated with keys that start with this prefix.
To accomplish this, implement a class MapSum:
Constructor: Initializes the object.
void insert (String key, int val): Inserts the key-value pair into the data structure. If the key already exists, its value is updated to the new one.
int sum (String prefix): Returns the total sum of values for all keys that begin with the specified prefix.
Constraints:
key.length,prefix.length...