476. Number Complement

Description

The complement of an integer is the integer you get when you flip all the 0's to 1's and all the 1's to 0's in its binary representation.

  • For example, The integer 5 is "101" in binary and its complement is "010" which is the integer 2.

Given an integer num, return its complement.

 

Example 1:

Input: num = 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: num = 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.

 

Constraints:

  • 1 <= num < 231

 

Note: This question is the same as 1009: https://leetcode.com/problems/complement-of-base-10-integer/

Solutions

Solution 1

Python Code
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class Solution:
    def findComplement(self, num: int) -> int:
        ans = 0
        find = False
        for i in range(30, -1, -1):
            b = num & (1 << i)
            if not find and b == 0:
                continue
            find = True
            if b == 0:
                ans |= 1 << i
        return ans

Java Code
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class Solution {
    public int findComplement(int num) {
        int ans = 0;
        boolean find = false;
        for (int i = 30; i >= 0; --i) {
            int b = num & (1 << i);
            if (!find && b == 0) {
                continue;
            }
            find = true;
            if (b == 0) {
                ans |= (1 << i);
            }
        }
        return ans;
    }
}

C++ Code
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class Solution {
public:
    int findComplement(int num) {
        int full = pow(2, int(log2(num)) + 1) - 1;
        return full ^ num;
    }
};

Go Code
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func findComplement(num int) int {
	ans := 0
	find := false
	for i := 30; i >= 0; i-- {
		b := num & (1 << i)
		if !find && b == 0 {
			continue
		}
		find = true
		if b == 0 {
			ans |= (1 << i)
		}
	}
	return ans
}

Solution 2

Python Code
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class Solution:
    def findComplement(self, num: int) -> int:
        return num ^ (2 ** (len(bin(num)[2:])) - 1)

C++ Code
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class Solution {
public:
    int findComplement(int num) {
        int ans = 0;
        bool find = false;
        for (int i = 30; i >= 0; --i) {
            int b = num & (1 << i);
            if (!find && b == 0) continue;
            find = true;
            if (b == 0) ans |= (1 << i);
        }
        return ans;
    }
};