leetcode 717. 1-bit and 2-bit Characters ( Python )

描述

We have two special characters. The first character can be represented by one bit 0. The second character can be represented by two bits (10 or 11).

Now given a string represented by several bits. Return whether the last character must be a one-bit character or not. The given string will always end with a zero.

Example 1:

Input: 
bits = [1, 0, 0]
Output: True
Explanation: 
The only way to decode it is two-bit character and one-bit 	character. So the last character is one-bit character.

Example 2:

Input: 
bits = [1, 1, 1, 0]
Output: False
Explanation: 
The only way to decode it is two-bit character and two-bit character. So the last character is NOT one-bit character.

Note:

1 <= len(bits) <= 1000.
bits[i] is always 0 or 1.

解析

根据题意一共有三种数字组合：10、11、0，判断最后一个数字是否是一个单独的数组，用到了贪心算法，设置一个变量 i ，遍历数组碰到 1 ，不管后面一位是什么，都是一个合法的两位数，所以直接 i+2 ，如果碰到 0，则 i+1 ，遍历范围是 i<len(bits)-1，最后判断是否 i==len(bits)-1 。时间复杂度为 O(N)，空间复杂度为 O(1)。

解答

class Solution(object):
def isOneBitCharacter(self, bits):
    """
    :type bits: List[int]
    :rtype: bool
    """
    i = 0
    while i<len(bits)-1:
        if bits[i] == 0:
            i+=1
        else:
            i+=2
    return i == len(bits)-1 
                   

运行结果

Runtime: 48 ms, faster than 17.47% of Python online submissions for 1-bit and 2-bit Characters.
Memory Usage: 11.9 MB, less than 15.00% of Python online submissions for 1-bit and 2-bit Characters.

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