Question

How to set the rightmost unset bit in a number in C

Answer 1

#include <stdio.h>

void show_bits(int n, int size) {
    for (int i = 1 << (size - 1); i > 0; i = i / 2)
        (n & i) ? printf("1") : printf("0");
}

int setRightmostUnsetBit(int n) {
    if ((n & (n + 1)) == 0)
        return n;

    return n | (n + 1);
}

int main() {
    int n = 25;

    show_bits(n, 8);

    printf("\n");

    show_bits(setRightmostUnsetBit(n), 8);

    return 0;
}




/*
run:

00011001
00011011

*/

 

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