A curated list of awesome bitwise operations and tricks
Maintainer - Keon Kim Please feel free to pull requests
Set nth bit
x | (1<<n)
Unset nth bit
x & ~(1<<n)
Toggle nth bit
x ^ (1<<n)
Round up to the next power of two
unsigned int v; //only works if v is 32 bit
v--;
v |= v >> 1;
v |= v >> 2;
v |= v >> 4;
v |= v >> 8;
v |= v >> 16;
v++;
Get the maximum integer
int maxInt = ~(1 << 31);
int maxInt = (1 << 31) - 1;
int maxInt = (1 << -1) - 1;
Get the minimum integer
int minInt = 1 << 31;
int minInt = 1 << -1;
Get the maximum long
long maxLong = ((long)1 << 127) - 1;
Multiply by 2
n << 1; // n*2
Divide by 2
n >> 1; // n/2
Multiply by the mth power of 2
n << m;
Divide by the mth power of 2
n >> m;
Check Equality
This is 35% faster in Javascript
(a^b) == 0; // a == b
Check if a number is odd
(n & 1) == 1;
Exchange (swap) two values
a ^= b;
b ^= a;
a ^= b;
Get the absolute value
//version 1
x < 0 ? -x : x;
//version 2
(x ^ (x >> 31)) - (x >> 31);
Get the max of two values
b & ((a-b) >> 31) | a & (~(a-b) >> 31);
Get the min of two values
a & ((a-b) >> 31) | b & (~(a-b) >> 31);
Check whether both numbers have the same sign
(x ^ y) >= 0;
Flip the sign
i = ~i + 1; // or
i = (i ^ -1) + 1; // i = -i
Calculate 2n
2 << (n-1);
Whether a number is some factorial of 2
n > 0 && (n & (n - 1)) == 0;
Modulo 2n against m
m & (n - 1);
Get the average
(x + y) >> 1;
((x ^ y) >> 1) + (x & y);
Get the mth bit of n (from low to high)
(n >> (m-1)) & 1;
Set the mth bit of n to 0 (from low to high)
n & ~(1 << (m-1));
Check if nth bit is set
if (x & (1<<n)) {
n-th bit is set
} else {
n-th bit is not set
}
Isolate (extract) the right-most 1 bit
x & (-x)
Isolate (extract) the right-most 0 bit
~x & (x+1)
Set the right-most 0 bit to 1
x | (x+1)
n + 1
-~n
n - 1
~-n
Get the negative value of a number
~n + 1;
(n ^ -1) + 1;
if (x == a) x = b; if (x == b) x = a;
x = a ^ b ^ x;
Convert letter to lowercase:
OR by space => (x | ' ')
Result is always lowercase even if letter is already lowercase
eg. ('a' | ' ') => 'a' ; ('A' | ' ') => 'a'
Convert letter to uppercase:
AND by underline => (x & '_')
Result is always uppercase even if letter is already uppercase
eg. ('a' & '_') => 'A' ; ('A' & '_') => 'A'
Invert letter's case:
XOR by space => (x ^ ' ')
eg. ('a' ^ ' ') => 'A' ; ('A' ^ ' ') => 'a'
Letter's position in alphabet:
AND by chr(31)/binary('11111')/(hex('1F') => (x & "\x1F")
Result is in 1..26 range, letter case is not important
eg. ('a' & "\x1F") => 1 ; ('B' & "\x1F") => 2
Get letter's position in alphabet (for Uppercase letters only):
AND by ? => (x & '?') or XOR by @ => (x ^ '@')
eg. ('C' & '?') => 3 ; ('Z' ^ '@') => 26
Get letter's position in alphabet (for lowercase letters only):
XOR by backtick/chr(96)/binary('1100000')/hex('60') => (x ^ '`')
eg. ('d' ^ '`') => 4 ; ('x' ^ '`') => 25
Fast color conversion from R5G5B5 to R8G8B8 pixel format using shifts
R8 = (R5 << 3) | (R5 >> 2)
G8 = (R5 << 3) | (R5 >> 2)
B8 = (R5 << 3) | (R5 >> 2)
Note: using anything other than the English letters will produce garbage results
For more Complicated Stuffs Read This