677.md

677. Map Sum Pairs

Implement a MapSum class with insert, and sum methods.

For the method insert, you'll be given a pair of (string, integer). The string represents the key and the integer represents the value. If the key already existed, then the original key-value pair will be overridden to the new one.

For the method sum, you'll be given a string representing the prefix, and you need to return the sum of all the pairs' value whose key starts with the prefix.

Example 1:
Input: insert("apple", 3), Output: Null
Input: sum("ap"), Output: 3
Input: insert("app", 2), Output: Null
Input: sum("ap"), Output: 5

my thoughts:

1. create a hash map, insert will either insert or update val; sum will search through keys and sum up the vals.

my solution:

**********29ms
class MapSum(object):

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.d = {}

    def insert(self, key, val):
        """
        :type key: str
        :type val: int
        :rtype: void
        """
        self.d[key] = val

    def sum(self, prefix):
        """
        :type prefix: str
        :rtype: int
        """
        res = 0
        l = len(prefix)
        for k in self.d.keys():
            if len(k)>=l and k[:l] == prefix:
                res += self.d[k]
        return res


# Your MapSum object will be instantiated and called as such:
# obj = MapSum()
# obj.insert(key,val)
# param_2 = obj.sum(prefix)

my comments:

from other ppl's solution:

1. N/A