677. Map Sum Pairs LeetCode Solution | Easy Approach

Minimum Cost to Merge Stones

Map Sum Pairs Design a map that allows you to do the following:

  • Maps a string key to a given value.
  • Returns the sum of the values that have a key with a prefix equal to a given string.

Implement the MapSum class:

  • 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.

Example 1:

["MapSum", "insert", "sum", "insert", "sum"]
[[], ["apple", 3], ["ap"], ["app", 2], ["ap"]]
[null, null, 3, null, 5]

Explanation 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.

Map Sum Pairs Solutions

Time: O(n)
Space: O(n)


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