原題鏈接在這里：https://leetcode.com/problems/number-complement/

題目：

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.

題解：

找到num最左面的1 bit, 從這個位置到最后是要flip的部分. template是從最左位置到最后到時1 bit.?

flip原來整體的num, 然后位運算 & template.

Time Complexity: O(1). Space: O(1).

AC Java:

1 public class Solution { 2 public int findComplement(int num) { 3 int template = (Integer.highestOneBit(num) << 1) - 1; 4 num = ~num; 5 return num & template; 6 } 7 }

?

轉載于:https://www.cnblogs.com/Dylan-Java-NYC/p/6272363.html

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