Merge pull request TheAlgorithms#90 from varunu28/master

dynamitechetan · web-flow · commit 35b17aaa0d69 · 2017-09-10T15:08:08.000+05:30
Added Fibanacci using memoization
diff --git a/Dynamic Programming/Fibonacci.java b/Dynamic Programming/Fibonacci.java
@@ -0,0 +1,75 @@
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ *
+ * @author Varun Upadhyay (https://github.com/varunu28)
+ *
+ */
+
+public class Fibonacci {
+
+    public static Map<Integer,Integer> map = new HashMap<Integer,Integer>();
+
+    public static void main(String[] args) throws Exception {
+
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int n = Integer.parseInt(br.readLine());
+
+        System.out.println(fibMemo(n)); // Returns 8 for n = 6
+        System.out.println(fibBotUp(n)); // Returns 8 for n = 6
+    }
+
+    /**
+     * This method finds the nth fibonacci number using memoization technique
+     *
+     * @param n The input n for which we have to determine the fibonacci number
+     * Outputs the nth fibonacci number
+     **/
+
+    public static int fibMemo(int n) {
+        if (map.containsKey(n)) {
+            return map.get(n);
+        }
+
+        int f;
+
+        if (n <= 2) {
+            f = 1;
+        }
+        else {
+            f = fib(n-1) + fib(n-2);
+            map.put(n,f);
+        }
+
+        return f;
+    }
+
+    /**
+     * This method finds the nth fibonacci number using bottom up
+     *
+     * @param n The input n for which we have to determine the fibonacci number
+     * Outputs the nth fibonacci number
+     **/
+
+    public static int fibBotUp(int n) {
+
+        Map<Integer,Integer> fib = new HashMap<Integer,Integer>();
+
+        for (int i=1;i<n+1;i++) {
+            int f = 1;
+            if (i<=2) {
+                f = 1;
+            }
+            else {
+                f = fib.get(i-1) + fib.get(i-2);
+            }
+            fib.put(i, f);
+        }
+
+        return fib.get(n);
+    }
+}
+
