LC717. 1-bit and 2-bit Characters

class Solution:
    def isOneBitCharacter(self, bits: List[int]) -> bool:
        """tc O(N) sc(N)
        """
        start = 0
        end = len(bits) -1 
        def dfs(s,e):
            if s > e :
                return True
            if bits[s] == 0:
                return True and dfs(s+1,e)
            elif e-s >1 and bits[s] == 1:
                return True and dfs(s+2,e)
            return False
        return dfs(start,end)

class Solution:
    def isOneBitCharacter(self, bits: List[int]) -> bool:
        """tc O(N) sc(1)
        to distinguish 2 bits or 1 bit is first bit if its 1 or 0  => i as a ptr to jump 1 step or 2 step based on its value
        1. go through bits [:-1]
        2. keep increment i by at least 1 as well as i's current val 
        3. if i arrive right at n-1 position means last bits size is 1 
        """
        i = 0
        n = len(bits)
        while i < n-1:
            i += bits[i]+1
        return i == n-1