bitsmap.cpp

#define BITSPERWORD sizeof(int)*8
#define SHIFT 5
#define MASK 0x1f
#define N 10000000
int a[1+N/BITSPERWORD];

void set(int i){
    a[i/BITSPERWORD]|=(1<<(i%BITSPERWORD));
}

void clr(int i){
    a[i/BITSPERWORD]&=~(1<<(i%BITSPERWORD));
}

int test(int i){
    return a[i/BITSPERWORD]&(1<<(i%BITSPERWORD));
}