C程序设置数字N的第K位

给定一个数N和一个整数K ，任务是设置数N的第 K 位，即如果第 K 位为 0，则将其设置为 1，如果为 1，则保持不变。

例子：

Input: N = 5, K = 2
Output: 7
Explanation: 
5 is represented as 101 in binary and has its second bit 0, so setting it will result in 111 i.e. 7.

Input: N = 5, K = 1
Output: 5
Explanation: 
5 is represented as 101 in binary and has its first bit is already 1, so setting it will result in 101 i.e. 5.

方法：解决这个问题的方法是基于位掩码技术，借助按位或运算符。

• 由于任何位与设置位的按位或会导致设置位，即
  

  Any bit   Set bit = Set bit

  which means,

  0 | 1 = 1

  1 | 1 = 1

• 因此，对于设置位，最好的办法是对设置的位执行数字的按位或。
  

  n = n | 1 << K

  OR

  n |= 1 << K

  where K is the bit that is to be set

下面是实现上述方法的 C++ 程序——

C++

// C++ program to implement the above approach
#include 
  
// Function to set the
// kth bit of n
int setBit(int N, int K)
{
    return (N | (1 << (K - 1)));
}
  
// Driver code
int main()
{
    int N = 5, K = 2;
    printf("%d\n", setBit(N, K));
    return 0;
}

输出

7