LeetCode_Easy_471:Number Complement
题目描述
Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.
Note:
- The given integer is guaranteed to fit within the range of a 32-bit signed integer.
- You could assume no leading zero bit in the integer’s binary representation.
Example 1:
Input: 5
Output: 2
Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.
Example 2:
Input: 1
Output: 0
Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.
思路笔记
高效解
我能想到的直观思路,就是在二进制转十进制的时候将各位余数数值取反,然后再转换为十进制。
但是知道我看到了最优解:Java 1 line bit manipulation solution(仅仅一句话代码)
public int findComplement(int num) {
return ~num & ((Integer.highestOneBit(num) << 1) - 1);
}
收获:与非位运算
我们首先要理解位运算:
说明:
位运算包括:“与”、“非”、“或”、“异或”。
运算符主要针对两个二进制数的位进行逻辑运算。
非:
与:
然后我们总结一下一句话代码:
- 假设Num=5(101),我们求出其非值为(11111111111111111111111111111010)这是一个32位的值,可是我们只想要其后三位。
- Integer.highestOneBit(num) << 1) - 1,可以快速求出和其长度相同的且各位为1的值,即111。
- 两者求与,剩下的就是010。
05-16 12:57