The following function is claimed to evaluate whether a number is integer power of 4. I do not quite understand how it works?
bool fn(unsigned int x)
{
if ( x == 0 ) return false;
if ( x & (x - 1) ) return false;
return x & 0x55555555;
}
evaluate whether a number is integer power of 4
Viewed 6497
4 Answers
Below solution works for 2,4,16 power of checking.
public static boolean isPowerOf(int a, int b)
{
while(b!=0 && (a^b)!=0)
{
b = b << 1;
}
return (b!=0)?true:false;
}
isPowerOf(4,2) > true
isPowerOf(8,2) > true
isPowerOf(8,3) > false
isPowerOf(16,4) > true
var isPowerOfFour = function (n) {
let x = Math.log(n) / Math.log(4)
if (Number.isInteger(x)) {
return true;
}
else {
return false
}
};
isPowerOfFour(4) ->true
isPowerOfFour(1) ->true
isPowerOfFour(5) ->false
Related