Bit Manipulation — Useful Tricks for efficient coding.

• Create a number that has only set bit as k-th bit -- 1 << (k-1)

• Check whether k-th bit is set or not --

    if (n & (1 << (k - 1)))
      cout << "SET";

• Set k-th bit to 1 -- n | (1 << (k - 1))

• Clearing the k-th bit -- n & ~(1 << (k - 1))

• Toggling the k-th bit -- n ^ (1 << (k – 1))

• Check whether n is power of 2 or not

    if(x && (!( x&(x-1) ))
      cout<<"Power of 2";

• (x<<y) is equivalent to multiplying x with 2^y (2 raised to power y).

• (x>>y) is equivalent to dividing x with 2^y.

• Swapping two numbers

    x = x ^ y
    y = x ^ y
    x = x ^ y

• Average of two numbers -- (x+y) >> 1

• Convert character ch from Upper to Lower case -- ch = ch | ' '

• Convert character ch from Lower to Upper case -- ch = ch & '_'

• Check if n is odd or even --

    if(n & 1)
      cout<<"odd"
    else
      cout<<"even";

Bitwise operations are very useful as they mostly operate in O(1) time. Please upvote if its helpful and suggestions are welcome.