bitmap实现

#include <stdio.h>

#define BITS 32

#define MASK 0x1F

#define SHIFT 5

#define N 10000000 //支持N位的bit

int a[1+N/BITS];

void set(int i) {a[i>>SHIFT] |= (1<<(i&MASK));}

void clr(int i) {a[i>>SHIFT] &= ~(1<<(i&MASK));}

int test(int i) {return a[i>>SHIFT] & (1<<(i&MASK));}

void bit_print(int n){

int mask = 1<<(BITS-1);

for (int i = 1; i <= BITS; i++){

putchar((n&mask) == 0?'0':'1');

n <<= 1;

}

}

/////////////////////////

int main()

{

set(5);

set(15);

bit_print(a[0]);

putchar('\n');

clr(15);

bit_print(a[0]);

putchar('\n');

printf("%d, %d", test(5), test(15) );

getchar();

}