[每日 LeetCode] 717. 1-bit and 2-bit Characters

Description:

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.

思路：本题意思是有两种字符，一种是 0，一种是 10 或者 11，现在要判断整个数组是否由这两种组成的，要求最后一位的数字必须是单个的 0。比较简单，直接扫描数组，如果元素值为 0 则前进一步，为 1 则前进两步，最后判断当前位置是否是倒数第二的位置。

C++ 代码

class Solution {
public:
    bool isOneBitCharacter(vector<int>& bits) {
        int n = bits.size(), i = 0;
        while (i < n - 1) {
            if (bits[i] == 0) 
                ++i;
            else 
                i+= 2;
        }
        return i == n - 1;
    }
};

运行时间：4ms

运行内存：8.7M