Bit manipulations

1. Multiply two Numbers Without Using * Operator

m=0; while (a) { if (a&1) m+=b; a>>=1; b<<=1; } return m;

1. check number is even or odd

http://www.programmingsimplified.com/c/source-code/c-program-check-odd-even

1. check if a num is power of 2

public class Solution { public boolean isPowerOfTwo(int n) { if(n<=0) return false; while(n>2){ int t = n>>1; int c = t<<1; if(n-c="" !="0)" return="" false;="" n="n">>1; } return true; } }

solution II:

public class Solution { public boolean isPowerOfTwo(int n) { if(n<=0) return false; return ((n & n-1) == 0); } }

1. check a number is positive or negative

int k = (a >> 31) & 1; k == 1 negative, k == 0 positive

1. find max of two numbers without comparison

check Cracking coding interview at page 476

int findMax( int x, int y) { int z = x - y; int i = (z >> 31) & 0x1; int max = x - i * z; return max; }