求一个整数是否是2的n次方

awk版:

gawk '$1>1 && !and($1,$1-1){print "YES";i=1}END{if(!i)print "NO"}'

C版:

#include <stdio.h>

int is2n(unsigned int i){
    return i>1 && !(i&(i-1));
}

int main(void){
    unsigned int i, c;
    scanf("%d", &i);

    switch(is2n(i)){
        case 0:
            printf("NO\n");
            break;
        case 1:
            printf("YES\n");
            break;
    }

    return 0;
}