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| #include <stdio.h>
#include <time.h>
#include <stdlib.h>
unsigned int pow2sup(unsigned int nbr)
{
int bs,bi;
int min = 0;
int max = 31;
int mid = (min + max)/2;
/* Borne inferieure */
if(nbr <= 1) {
return 1;
}
/* Borne superieure */
if( nbr > (1<<30)) {
return (1<<31);
}
do
{
bs = (1<<mid);
bi = (1<<(mid-1));
if(nbr < bi) {
max = mid;
mid = (min+max)/2;
}
else {
if(nbr > bs) {
min = mid;
mid = (min+max)/2;
}
else {
if(bi == nbr) {
return bi;
}
return bs;
}
}
}while(min != max);
return 0;
}
int main(void)
{
int i;
unsigned int nbr,sol;
srand(time(NULL));
for(i=0;i<30;i++) {
nbr = rand();
sol = pow2sup(nbr);
if((sol >= nbr) && (sol/2 < nbr)) {
printf("%u -> %u \n",nbr,sol);
}
else {
printf("Erreur avec %u -> %u\n",nbr, sol);
}
}
return EXIT_SUCCESS;
} |
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