Minimum Flips to Make a OR b Equal to c in C++

Suppose we have 3 positives numbers a, b and c. We have to find the minimum flips required in some bits of a and b to make (a OR b == c ). Here we are considering bitwise OR operation.

The flip operation consists of change any single bit 1 to 0 or change the bit 0 to 1 in their binary representation. So if a : 0010 and b := 0110, so c is 0101, After flips, a will be 0001, and b will be 0100

To solve this, we will follow these steps −

• ans := 0
• for i in range 0 to 31
  • bitC := (c / 2^i) AND 1
  • bitA := (a / 2^i) AND 1
  • bitB := (b / 2^i) AND 1
  • if (bitA OR bitB) is not same as bitC, then
    • if bitC is 0
      • if bitA = 1 and bitB = 1, then increase ans by 2, otherwise increase ans by 1
    • otherwise increase ans by 1
• return ans

Example

Let us see the following implementation to get better understanding −

class Solution {
   public:
   int minFlips(int a, int b, int c) {
      int ans = 0;
      for(int i = 0; i < 32; i++){
         int bitC = (c >> i) & 1;
         int bitA = (a >> i) & 1;
         int bitB = (b >> i) & 1;
         if((bitA || bitB) != bitC){
            if(!bitC){
               if(bitA == 1 && bitB == 1){
                  ans += 2;
               } else {
                  ans += 1;
               }
            } else {
               ans += 1;
            }
         }
      }
      return ans;
   }
};

Input

2
6
5

Output

3

Arnab Chakraborty

Published on 18-Mar-2020 05:52:01