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  1. #include <stdio.h>
  2.  
  3. 	int isPositive(int x) { return ((~x & (~x + 1)) >> 31) & 1; }
  4.  
  5. 	int isPowerOfTwo(int x) { return isPositive(x) & ~(x & (x-1)); }
  6.  
  7. 	int log2(int x)
  8. 	{
  9. 		int i = (-1);
  10. 		while(isPositive(x)) i++, x >>= 1;
  11. 		return i;
  12. 	}
  13.  
  14. 	int isPowerOfNegativeTwo(int x)
  15. 	{
  16. 		return (  isPositive(x) &  isPowerOfTwo(x) & ~(log2(x) % 2) )
  17. 			 | ( ~isPositive(x) & isPowerOfTwo(-x) & (log2(-x) % 2) );
  18. 	}
  19.  
  20. int main(void)
  21. {
  22. 	int x = 256;
  23. 	printf("%s", isPowerOfNegativeTwo(-512)?"true":"false");
  24. 	//printf("%s",( isPositive(x) & isPowerOfTwo(x)  & ~(log2(x) % 2) )?"true":"false");
  25. 	return 0;
  26. }
  27.  
Success #stdin #stdout 0s 9432KB
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https://ideone.com/6ey9Cw
language:
C (gcc 8.3)
created:
7 years ago
visibility:
public

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