BitMapTest.java

package bit;

import org.junit.Test;

import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;

public class BitMapTest {

 /*
 TASK
 O(1)으로 해당 데이터가 존재하는지 판단한다.
 */

 @Test
 public void test() {
 BitMap bitMap = new BitMap();
 bitMap.store("1234567");
 assertThat(bitMap.exist("1234567"), is(true));
 assertThat(bitMap.exist("1234568"), is(false));
 }

 public class BitMap {
 public int[] cache;

 public BitMap() {
 cache = new int[(10 * 1000 * 1000) / 32];
 }

 public void store(String data) {
 int dataInt = Integer.parseInt(data);
 int arrIndex = dataInt / 32;
 int byteIndex = dataInt % 32;
 cache[arrIndex] = cache[arrIndex] | (1 << byteIndex);
 }

 public boolean exist(String data) {
 int dataInt = Integer.parseInt(data);
 int arrIndex = dataInt / 32;
 int byteIndex = dataInt % 32;
 return (cache[arrIndex] & (1 << byteIndex)) != 0;
 }
 }
}