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Formatted question description: https://leetcode.ca/all/1318.html

1318. Minimum Flips to Make a OR b Equal to c (Medium)

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.

 

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

 

Constraints:

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

Related Topics:
Bit Manipulation

Solution 1.

  • class Solution {
        public int minFlips(int a, int b, int c) {
            int flips = 0;
            StringBuffer aBinarySB = new StringBuffer(Integer.toBinaryString(a));
            StringBuffer bBinarySB = new StringBuffer(Integer.toBinaryString(b));
            StringBuffer cBinarySB = new StringBuffer(Integer.toBinaryString(c));
            while (aBinarySB.length() < 32)
                aBinarySB.insert(0, '0');
            while (bBinarySB.length() < 32)
                bBinarySB.insert(0, '0');
            while (cBinarySB.length() < 32)
                cBinarySB.insert(0, '0');
            for (int i = 0; i < 32; i++) {
                char aChar = aBinarySB.charAt(i);
                char bChar = bBinarySB.charAt(i);
                char cChar = cBinarySB.charAt(i);
                if (cChar == '0') {
                    if (aChar == '1')
                        flips++;
                    if (bChar == '1')
                        flips++;
                } else {
                    if (aChar == '0' && bChar == '0')
                        flips++;
                }
            }
            return flips;
        }
    }
    
    ############
    
    class Solution {
        public int minFlips(int a, int b, int c) {
            int ans = 0;
            for (int i = 0; i < 30; ++i) {
                int x = a >> i & 1, y = b >> i & 1, z = c >> i & 1;
                if ((x | y) != z) {
                    ans += x == 1 && y == 1 ? 2 : 1;
                }
            }
            return ans;
        }
    }
    
  • // OJ: https://leetcode.com/problems/minimum-flips-to-make-a-or-b-equal-to-c/
    // Time: O(1)
    // Space: O(1)
    class Solution {
    public:
        int minFlips(int a, int b, int c) {
            int ans = 0;
            for (int i = 0; i < 31; ++i) {
                if ((c >> i) & 1) ans += ((a >> i) & 1) == 0 && ((b >> i) & 1) == 0;
                else ans += ((a >> i) & 1) + ((b >> i) & 1);
            }
            return ans;
        }
    };
    
  • class Solution:
        def minFlips(self, a: int, b: int, c: int) -> int:
            ans = 0
            for i in range(31):
                x, y, z = (a >> i) & 1, (b >> i) & 1, (c >> i) & 1
                if (x | y) == z:
                    continue
                if x == 1 and y == 1 and z == 0:
                    ans += 2
                else:
                    ans += 1
            return ans
    
    
    
  • func minFlips(a int, b int, c int) (ans int) {
    	for i := 0; i < 30; i++ {
    		x, y, z := a>>i&1, b>>i&1, c>>i&1
    		if (x | y) != z {
    			if x == 1 && y == 1 {
    				ans += 2
    			} else {
    				ans++
    			}
    		}
    	}
    	return
    }
    

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