23dfcca431 2011-02-23        kinaba: int bitcnt(LL x)
23dfcca431 2011-02-23        kinaba: {
23dfcca431 2011-02-23        kinaba: 	int c = 0;
23dfcca431 2011-02-23        kinaba: 	for(; x; x>>=1)
23dfcca431 2011-02-23        kinaba: 		c += x&1;
23dfcca431 2011-02-23        kinaba: 	return c;
23dfcca431 2011-02-23        kinaba: }
8f8efc5938 2013-06-27        kinaba: 
8f8efc5938 2013-06-27        kinaba: 
8f8efc5938 2013-06-27        kinaba: /* for every nonempty subset of S  : O(2^|S|)
8f8efc5938 2013-06-27        kinaba:  for(int sub=S; sub; sub=(sub-1)&S) { ... }
8f8efc5938 2013-06-27        kinaba: 
8f8efc5938 2013-06-27        kinaba: */