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  • leetcode 1318 Minimum Flips to Make a OR b Equal to c

    Given 3 positives numbers ab 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

    题目大意:给定三个数a, b, c,对a,b,c的二进制表示,每修改二进制比特中的一位为1次,返回修改a和b的最少次数,使得a or b = c.

    思路:我们先计算a or b, 然后让其结果的二进制和c的二进制一位一位的进行比较,如果某一位不同,则需要修改a或者b,假如某一位c为0, 而a or b对应的为1,则要考虑a和b对应的是不是都为1,如果都为1,则都要改,修改次数加2,否则只要修改一个,如果某一位c为1,则只要修改a或者b中那一位为1,修改次数加1.

     1 class Solution {
     2 public:
     3     int minFlips(int a, int b, int c) {
     4         int cnt = 0;
     5         int A = a | b;
     6         while (A || c) {
     7             int d1 = c & 1, d2 = A & 1;
     8             if (d1 != d2) {
     9                 if ((d1 == 0) && ((a & 1) == 1 && (b & 1) == 1))
    10                     cnt += 2;
    11                 else
    12                     cnt++;
    13             }
    14             c >>= 1;
    15             A >>= 1;
    16             a >>= 1;
    17             b >>= 1;
    18         }
    19         return cnt;
    20     }
    21 };
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  • 原文地址:https://www.cnblogs.com/qinduanyinghua/p/12187628.html
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