1 package Today;
2 //LeetCode:476. Number Complement
3 /*
4 Given a positive integer, output its complement number.
5 The complement strategy is to flip the bits of its binary representation.
6
7 Note:
8 The given integer is guaranteed to fit within the range of a 32-bit signed integer.
9 You could assume no leading zero bit in the integer’s binary representation.
10 Example 1:
11 Input: 5
12 Output: 2
13 Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.
14 Example 2:
15 Input: 1
16 Output: 0
17 Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.
18 */
19 public class findComplement476 {
20 public static int findComplement(int num) {
21 int bits=0;
22 int number=num;
23 while(number>0){
24 bits++;
25 number=number>>1;
26 }
27 return num^(int)(Math.pow(2,bits)-1);
28 }
29 //study 原来有方法可以直接得到最高bit位
30 public static int findComplement2(int num){
31 return num^((Integer.highestOneBit(num)<<1)-1);
32 }
33 public static void main(String[] args) {
34 //TODO Auto-generated method stub
35 System.out.println(findComplement(5));
36 System.out.println(findComplement(1));
37 System.out.println(findComplement2(5));
38 System.out.println(findComplement2(1));
39
40 }
41
42 }
