Restore IP Addresses

def restoreIpAddresses(s: str):
    def backtrack(s, integers, path, result):
        if integers == 4:
            if not s:
                # we have 4 integers and
                # we've used all the digits in s
                result.append(path[:-1])
            return
        for i in range(1, 4):
            if i > len(s):
                continue
            # integer cannot have leading 0s
            if i > 1 and s[0] == '0':
                continue
            # integer must be less than 255
            if i > 2 and int(s[:3]) > 255:
                continue
            backtrack(s[i:], integers+1, path + s[:i] + '.', result)

    result = []
    backtrack(s, 0, '', result)
    return result