Problem
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
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.
Solution1 (My Solution)
class Solution {
public:
int findComplement(int num) {
std::bitset<32> bits(num);
int endPos = ignoreLeadingZero(bits);
for (int i = 0; i <= endPos; i++){
bits[i] = !bits[i];
}
return int(bits.to_ulong());
}
private:
int ignoreLeadingZero(bitset<32>& bits){
size_t bitsLength = bits.size();
for (int i = bitsLength - 1; i >= 0; i--){
if (bits[i] == 0) continue;
else return i;
}
}
};
Solution2
class Solution {
public:
int findComplement(int num) {
unsigned mask = ~0;
while (num & mask) mask <<= 1;
return ~mask & ~num;
}
};
- Solution2 通过求其掩码的方式，基于二进制运算，速度较快。
