1318. Minimum Flips to Make a OR b Equal to c

1. Description

Given 3 positives numbers a, b and c. Return the minimum flips required in some bits of a and b to make ( a OR b == c ). (bitwise OR operation).
Flip operation consists of change any single bit 1 to 0 or change the bit 0 to 1 in their binary representation.

2. Example

Example 1

Input: a = 2, b = 6, c = 5
Output: 3
Explanation: After flips a = 1 , b = 4 , c = 5 such that (a OR b == c)

Example 2

Input: a = 4, b = 2, c = 7
Output: 1

Example 3

Input: a = 1, b = 2, c = 3
Output: 0

3. Constraints

• 1 <= a <= 10$^9$
• 1 <= b <= 10$^9$
• 1 <= c <= 10$^9$

4. Solutions

Bit Manipulation

Time complexity: O(1)
Space complexity: O(1)

class Solution {
public:
    int minFlips(int a, int b, int c) {
        int flip = 0;
        for (int i = 0; i < 31; ++i) {
            int abit = (a >> i) & 1;
            int bbit = (b >> i) & 1;
            int cbit = (c >> i) & 1;

            if (cbit == 1) {
                flip += (abit == 0 && bbit == 0);
            } else {
                flip += abit + bbit;
            }
        }

        return flip;
    }
};