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BitOperator.java

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package bit;

import org.junit.Test;

import static org.hamcrest.CoreMatchers.is;

import static org.junit.Assert.assertThat;

public class BitOperator {

@Test

public void test() {

assertThat(isPowerOf2(2), is(true));

assertThat(isPowerOf2(4), is(true));

assertThat(isPowerOf2(8), is(true));

assertThat(isPowerOf2(16), is(true));

assertThat(isPowerOf2(17), is(false));

}

public String testFunction() {

return "";

}

public boolean get(int n, int i) {

int mask = 1 << i;

return (n & mask) != 0;

}

public int set(int n, int i) {

int mask = 1 << i;

return n | mask;

}

public int clear(int n, int i) {

int mask = ~(1 << i);

return n & mask;

}

TASK

2의 제곱수인지 판별한다.

public boolean isPowerOf2(int n) {

// 10 == 2 => 2 - 1 == 1

// 100 == 4 => 4 - 1 == 11

// 1000 == 8 => 8 - 1 == 111

// 10000 == 16 => 16 - 1 == 1111

// n에서 1을 뺀다음에 n과 and 연산을 하면 모두 0이 된다.

return (n & (n - 1)) == 0;

}

TASK

두 수에서 다른 비트의 개수를 구한다.

public int getBitDiff(int a, int b) {

int diff = a ^ b; //XOR

int count = 0;

while (diff != 0) {

diff = diff & (diff - 1);

count++;

}

return count;

}