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476. Number Complement

2024-09-02 16:14:15   220人阅读

题目

Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.

Note:

  1. The given integer is guaranteed to fit within the range of a 32-bit signed integer.
  2. 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.

 

分析

将int的二进制表示中所有0变为1，1变为0

解答

解法1：（我）

例1：

          5: 00000000000000000000000000000101

        ~5: 11111111111111111111111111111010 (补码形式，原码是10000000000000000000000000000110，值为-6)

        -23: 11111111111111111111111111111000 (补码形式，原码是10000000000000000000000000001000，值为-23)

~5-(-23): 00000000000000000000000000000010 (值为2)

 

 

   int的最大值：01111111111111111111111111111111          231-1

int的非最小值：11111111111111111111111111111111       -(231-1)

   int的最小值：10000000000000000000000000000000        -231 （特殊：使用以前的-0的补码来表示, 所以-231并没有原码和反码表示）

例2：

               231-1: 01111111111111111111111111111111

          ~(231-1): 10000000000000000000000000000000 (值为-231)

                 -231: 10000000000000000000000000000000

~(231-1)-(-231): 00000000000000000000000000000000 (值为0)

注：此处~(231-1)-(-231)不能写为~(231-1)+231，因为int中正数231超出最大值范围，会被解析成231-1，而负数(-231)没有超出最小值范围

1 public class Solution {
2     public int findComplement(int num) {
3         return ~num-(int)-Math.pow(2,32-Integer.numberOfLeadingZeros(num));
4     }
5 }

 

476. Number Complement


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