Number Complement
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.
题意:给你一个正数,将其转换成各个位与之相反的数。
思路:我们可以找一个有效位和所给的数相同,且每一位都是1的数与之做异或运算,即可得到答案。
/** * * @Title: findComplement * @Description: Number Complement * @Example : 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. */ public int findComplement(int num) { int xorNum = 1; int n = num >> 1; while(n > 0){ xorNum = ((xorNum << 1) + 1); n = n >> 1; } return num ^ xorNum; }
需要注意的是位运算的优先级低于+运算,因此加了括号。