Add bit operator code

jbee37142 · jbee37142 · commit b52665a0f43a · 2017-06-01T10:04:48.000+09:00
diff --git a/src/test/java/bit/BitOperator.java b/src/test/java/bit/BitOperator.java
@@ -0,0 +1,66 @@
+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;
+    }
+}
