Get frist 0 / first 1 of bit-representation of integer
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#include <stdio.h>
#include <math.h>
#define CHAR_BIT 8
#define INT_BIT CHAR_BIT*sizeof(unsigned int)
void sb(unsigned int* a, unsigned char pos){
*a |= 1 << (INT_BIT-pos-1);
}
int getPosition(unsigned int a){
float logg = log2(a);
return (INT_BIT - (int)floor(logg)) - 1;
}
int main(void) {
unsigned int a = 0;
sb(&a, 1);
sb(&a, 2);
sb(&a, 3);
sb(&a, 5);
sb(&a, 6);
printf("Poisiton of first 1 is: %d\n", getPosition(a));
printf("Poisiton of first 0 is: %d\n", getPosition(~a));
return 0;
}
C
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