Given a floating point number, write a function to count set bits in its binary representation.

For example, floating point representation of 0.15625 has 6 set bits (See this). A typical C compiler uses single precision floating point format.

We can use the idea discussed here. The idea is to take address of the given floating point number in a pointer variable, typecast the pointer to char * type and process individual bytes one by one. We can easily count set bits in a char using the techniques discussed here.

Following is C implementation of the above idea.

#include <stdio.h> // A utility function to count set bits in a char. // Refer http://goo.gl/eHF6Y8 for details of this function. unsigned int countSetBitsChar(char n) { unsigned int count = 0; while (n) { n &= (n-1); count++; } return count; } // Returns set bits in binary representation of x unsigned int countSetBitsFloat(float x) { // Count number of chars (or bytes) in binary representation of float unsigned int n = sizeof(float)/sizeof(char); // typcast address of x to a char pointer char *ptr = (char *)&x; int count = 0; // To store the result for (int i = 0; i < n; i++) { count += countSetBitsChar(*ptr); ptr++; } return count; } // Driver program to test above function int main() { float x = 0.15625; printf ("Binary representation of %f has %u set bits ", x, countSetBitsFloat(x)); return 0; }

Output:

Binary representation of 0.156250 has 6 set bits

This article is contrbuted by **Vineet Gupta**. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above