Question

How to check if all the bits of a given integer are one in C

Answer 1

#include <stdio.h>
#include <stdbool.h>
 
bool all_bits_are_one(unsigned int n) {
    while (n > 0) {
        if ( (n & 1) == 0) {
            return false;
        }
        n = n >> 1;
    }
 
    return true;
}
 
 
int main() {
 
    unsigned int n = 28; // 00011100
 
    if (all_bits_are_one(n)) {
        printf("All bits are 1\n");
    }
    else {
        printf("Not all bits are 1\n");
    }
    
    n = 15; // 1111
 
    if (all_bits_are_one(n)) {
        printf("All bits are 1\n");
    }
    else {
        printf("Not all bits are 1\n");
    }
}
 
 
 
 
/*
run:
 
Not all bits are 1
All bits are 1
 
*/

 

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