String

• This is created because there are so many interesting string problems that do not really fit into any other categories, just straight up understanding the problem and implement/handle edge cases

https://leetcode.com/problems/group-shifted-strings

def groupStrings(self, strings: List[str]) -> List[List[str]]:
    # any 2 strings that have the same length and same character offset between then should be in the same group
    def getCharDiff(s):
        if len(s) == 1:
            return []

        diffs = []
        for i in range(1, len(s)):
            diff = (ord(s[i]) - ord(s[i - 1])) % 26
            diffs.append(diff)

        return diffs

    diffsMap = collections.defaultdict(list)

    for s in strings:
        diffs = getCharDiff(s)
        diffsMap[tuple(diffs)].append(s)

    return list(diffsMap.values())

https://leetcode.com/problems/valid-number

• Just if/else
• Keep track of defining variables/state that let us know immediately if it is invalid

def isNumber(self, s: str) -> bool:
    seenDot = False
    seenDigit = False
    seenExp = False

    for i in range(len(s)):
        if s[i].isdigit():
            seenDigit = True
        elif s[i] == ".":
            if seenDot or seenExp:
                return False
            seenDot = True
        elif s[i] in "+-":
            if i != 0 and s[i - 1] not in "Ee":
                return False
            seenDigit = False
        elif s[i] in "Ee":
            if seenExp or not seenDigit:
                return False
            seenExp = True
            seenDigit = False
        else:
            return False

    return seenDigit