ⓁⒸ ‧‧‧ 476. Number Complement

476. Number Complement 數字補數

❀ Origin

Problem

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.

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❀ 翻譯

問題

給定一個正整數, 輸出其補數.
補數的定義是翻轉其二進制數的每個代表位元.

注意

1. 給定的整數保證符合在 32 位元有號數的範圍內.
2. 你可以在整數的二進制表示裡假設其沒有前面的 0 位元.

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❀ Solution

JavaScript

/**
 * @param {number} num
 * @return {number}
 */

/**
 * XOR 相同為零 不同為一
 * NOR 理論上也可以, 只是目前不曉得如何在JS使用 NOR
 */
var findComplement = function(num) {
	// 先取得目標數的二進制的長度
	var binaryLength = num.toString(2).length;

	// 使用 Math.pow() , 取得全為 1 的數, 2的n次方 -1
	var TheAllOneNum = Math.pow(2, binaryLength) - 1;

	// 與其執行 NOR
	return num ^ TheAllOneNum;
};
console.log(findComplement(9));