power

Author: yangrubing

swordForOffer/src/main/java/problem11/Power.java

@@ -0,0 +1,48 @@
+package problem11;
+
+/**
+ * 求数值的整数次方
+ * 需要考虑的边界条件：
+ * 1. 0的0次方
+ * 2. exponent为负数
+ * 3. double的精度问题
+ * Created by bjyangrubing on 2016/8/16.
+ */
+public class Power
+{
+	public double power(double base, int exponent) throws Exception
+	{
+		double result = 0.0;
+		if (equal(base, 0.0) && exponent < 0)
+			throw new Exception("0的负数次幂无意义");
+		if (equal(exponent, 0))
+			return 1.0;
+		if (exponent < 0)
+		{
+			result = powerWithExponent(1.0 / base, -exponent);
+		}
+		else
+		{
+			result = powerWithExponent(base, exponent);
+		}
+		return result;
+	}
+
+	private double powerWithExponent(double base, int exponent)
+	{
+		double result = 1.0;
+		for (int i = 0; i < exponent; i++)
+		{
+			result *= base;
+		}
+		return result;
+	}
+
+	public boolean equal(double base, double v)
+	{
+		if ((base - v > -0.0000001) && (base - v < 0.0000001))
+			return true;
+		return false;
+	}
+
+}

swordForOffer/src/test/java/problem11/PowerTest.java

@@ -0,0 +1,16 @@
+package problem11;
+
+import org.junit.Test;
+
+/**
+ * Created by bjyangrubing on 2016/8/16.
+ */
+public class PowerTest
+{
+	@Test
+	public void test() throws Exception
+	{
+		Power power = new Power();
+		System.out.println(power.equal(power.power(2, 4), 16));
+	}
+}