solution.py

class AllOne:
    def __init__(self):
        self.myDict = {}

    def inc(self, key: str) -> None:
        if key in self.myDict:
            self.myDict[key] += 1
        else:
            self.myDict[key] = 1

    def dec(self, key: str) -> None:
        if key in self.myDict:
            if self.myDict[key] > 1:
                self.myDict[key] -= 1
            else:
                self.myDict.pop(key)

    def getMaxKey(self) -> str:
        if not self.myDict:
            return ""
        maxVal = max(self.myDict.values())
        for key in self.myDict.keys():
            if self.myDict[key] == maxVal:
                return key

    def getMinKey(self) -> str:
        if not self.myDict:
            return ""
        minVal = min(self.myDict.values())
        for key in self.myDict.keys():
            if self.myDict[key] == minVal:
                return key