fibnacci

Author: yangrubing

swordForOffer/src/main/java/problem09/Fibonacci.java

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+package problem09;
+
+/**斐波那契数列
+ * Created by bjyangrubing on 2016/8/16.
+ */
+public class Fibonacci
+{
+	/**
+	 * 递归的方式
+	 */
+	public int fib(int n)
+	{
+		if (n <= 0)
+		{
+			return 0;
+		}
+		if (n == 1)
+		{
+			return 1;
+		}
+		return fib(n - 1) + fib(n - 2);
+	}
+
+	/**
+	 * 非递归，递推的方式
+	 */
+	public int fib2(int n)
+	{
+		int[] result =
+		{ 0, 1 };
+		if (n < 2)
+			return result[n];
+		int fibNMinusOne = 1;
+		int fibNMinusTwo = 0;
+		int fibN = 0;
+		for (int i = 2; i <= n; i++)
+		{
+			fibN = fibNMinusOne + fibNMinusTwo;
+			fibNMinusTwo = fibNMinusOne;
+			fibNMinusOne = fibN;
+		}
+
+		return fibN;
+
+	}
+
+	public static void main(String args[])
+	{
+		System.out.println(new Fibonacci().fib2(5));
+	}
+}

swordForOffer/src/test/java/problem09/FibonacciTest.java

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+package problem09;
+
+import junit.framework.Assert;
+import org.junit.Test;
+
+/**
+ * Created by bjyangrubing on 2016/8/16.
+ */
+public class FibonacciTest
+{
+	@Test
+	public void test()
+	{
+		Fibonacci fibonacci = new Fibonacci();
+		Assert.assertEquals(5, fibonacci.fib(5));
+	}
+}