feat: fibonacci using dynamic programming (#223)

README.md

@@ -1330,6 +1330,24 @@ public class FibonacciSnippet {
     }
   }
 
+  /**
+   * Fibonacci series using dynamic programming. Works for larger ns as well.
+   *
+   * @param n given number
+   * @return fibonacci number for given n
+   */
+  public static int fibonacciBig(int n) {
+      int previous = 0;
+      int current = 1;
+      for (int i = 0; i < n - 1; i++) {
+          int t = previous + current;
+          previous = current;
+          current = t;
+      }
+
+      return current;
+  }
+
   /**
    * Example of what an iterative implementation of Fibonacci looks like.
    *

src/main/java/math/FibonacciSnippet.java

@@ -1,7 +1,7 @@
 /*
  * MIT License
  *
- * Copyright (c) 2017-2022 Ilkka Seppälä
+ * Copyright (c) 2017-2024 Ilkka Seppälä
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -46,6 +46,24 @@ public static int fibonacci(int n) {
     }
   }
 
+  /**
+   * Fibonacci series using dynamic programming. Works for larger ns as well.
+   *
+   * @param n given number
+   * @return fibonacci number for given n
+   */
+  public static int fibonacciBig(int n) {
+    int previous = 0;
+    int current = 1;
+    for (int i = 0; i < n - 1; i++) {
+      int t = previous + current;
+      previous = current;
+      current = t;
+    }
+
+    return current;
+  }
+
   /**
    * Example of what an iterative implementation of Fibonacci looks like.
    *

src/test/java/math/FibonacciSnippetTest.java

@@ -1,7 +1,7 @@
 /*
  * MIT License
  *
- * Copyright (c) 2017-2022 Ilkka Seppälä
+ * Copyright (c) 2017-2024 Ilkka Seppälä
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -51,6 +51,26 @@ void testFibonacci() {
     assertEquals(55, FibonacciSnippet.fibonacci(10));
   }
 
+  /**
+   * Tests for {@link FibonacciSnippet#fibonacciBig(int)}.
+   */
+  @Test
+  void testFibonacciBig() {
+    assertEquals(0, FibonacciSnippet.fibonacci(0));
+    assertEquals(1, FibonacciSnippet.fibonacci(1));
+    assertEquals(1, FibonacciSnippet.fibonacci(2));
+    assertEquals(2, FibonacciSnippet.fibonacci(3));
+    assertEquals(3, FibonacciSnippet.fibonacci(4));
+    assertEquals(5, FibonacciSnippet.fibonacci(5));
+    assertEquals(8, FibonacciSnippet.fibonacci(6));
+    assertEquals(13, FibonacciSnippet.fibonacci(7));
+    assertEquals(21, FibonacciSnippet.fibonacci(8));
+    assertEquals(34, FibonacciSnippet.fibonacci(9));
+    assertEquals(55, FibonacciSnippet.fibonacci(10));
+    assertEquals(6765, FibonacciSnippet.fibonacci(20));
+    assertEquals(102334155, FibonacciSnippet.fibonacci(40));
+  }
+
   /**
    * Tests for {@link FibonacciSnippet#iterativeFibonacci(int)}.
    */