Leetcode 677. Map Sum Pairs

  • MapSum() Initializes the MapSum object.
  • void insert(String key, int val) Inserts the key-val pair into the map. If the key already existed, the original key-value pair will be overridden to the new one.
  • int sum(string prefix) Returns the sum of all the pairs' value whose key starts with the prefix.
["MapSum", "insert", "sum", "insert", "sum"]
[[], ["apple", 3], ["ap"], ["app", 2], ["ap"]]
[null, null, 3, null, 5]
MapSum mapSum = new MapSum();
mapSum.insert("apple", 3);
mapSum.sum("ap"); // return 3 (apple = 3)
mapSum.insert("app", 2);
mapSum.sum("ap"); // return 5 (apple + app = 3 + 2 = 5)
  • 1 <= key.length, prefix.length <= 50
  • key and prefix consist of only lowercase English letters.
  • 1 <= val <= 1000
  • At most 50 calls will be made to insert and sum.
  1. use hashmap to store key String and the value
  2. use function: startsWith to check the prefix
  3. if String in the hashmap start with prefix, add them into the total count
  1. use TireNode to



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Gary Chiang

Gary Chiang

CS new grad, 6 years experience related to supply chain management. Located in Bay area