README.md

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.

Tags: Array

思路 1

观察可以发现，其实每个编码数组都只有一种解码方式，可以直接从头开始解码。

Java:

public boolean isOneBitCharacter(int[] bits) {
    int i = 0;
    while (i < bits.length - 1) {
        i += bits[i] + 1;
    }
    return i == bits.length - 1;
}

思路 2

再观察我们可以发现，0肯定是一个字符编码的结尾。且题目指出所给的编码数组的最后一个编码肯定为0，那么我们只要找到倒数第二个0的位置即可，因为这两个0之间的1的个数为偶数个时，当且仅当最后一个字符的编码为一个单独的0。

Java:

public boolean isOneBitCharacter(int[] bits) {
    int i = bits.length - 2;
    while (i >= 0 && bits[i] != 0) i--;
    return ((bits.length - i) & 1) == 0;
}

结语

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