Practice Map Sum Pairs

Read the task, work through the examples, and check your approach against the constraints. Use the original LeetCode task for coding and submissions.

Medium#677

LeetCode Problem

Map Sum Pairs

Hash Table String Design Trie

Problem Statement

MapSum.insert(key,val) maps a string key to an integer value, replacing an earlier value for that key. sum(prefix) adds values of all stored keys beginning with prefix and returns zero when none match. Practice approach: A trie can store the sum under each prefix. Keep previous complete-key values so replacement updates every prefix by the difference, not the full new value. Both operations then take O(L) for key or prefix length L. With the small call limit, scanning a normal map is also adequate. Test replacement and one key that is a prefix of another.

Source: Map Sum Pairs on LeetCode. Use the original task for its coding environment and submissions.

Examples

# Example 1

Input

["MapSum","insert","insert","sum","insert","sum","sum"]
[[],["car",4],["cart",7],["car"],["car",2],["car"],["z"]]

Output

[null,null,null,11,null,9,0]

Explanation

Replacing car changes its contribution from 4 to 2 while cart remains 7.

Constraints

1 <= key.length, prefix.length <= 50

Keys and prefixes contain lowercase letters.

1 <= val <= 1000

At most 50 total calls.

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