compute fibonacci

Recursion/Fibonacci.java

@@ -0,0 +1,49 @@
+public class Fibonacci {
+
+    //complexity  rootsqure(2) ^ n < x < (2 ^n+1)-1
+    public static int fibonacci1(int n) {
+        if(n == 0) return 1;
+        if(n == 1) return 1;
+
+        return (fibonacci1(n-1) + fibonacci1(n-2));
+    }
+
+    //b1 = 1, b2 = 1 , complexity linear
+    public static int fibonacci2(int n, int b1 ,int b2) {
+        int i = n;
+        while(i > 0 ) {
+            int temp = b1;
+            b1 = b1+b2;
+            b2 = temp;
+            i--;
+        }
+        return b1;
+    }
+//0(n) same as additive sequence
+    public static int fibonacciRe2(int n, int b1, int b2) {
+        if(n == 1) return b2; // or n == 0 return b1
+        return fibonacciRe2(n-1, b2, b1+b2);
+    }
+
+    public static int fibonacciDP(int n) {
+        int[] result = new int[n+1];
+        result[0] = 1;
+        result[1] = 1;
+        int i = 2;
+        while(i <= n) {
+            result[i] = result[i-1] + result[i-2];
+            i++;
+        }
+        return result[n];
+    }
+
+
+
+    public static void main(String[] args) {
+        System.out.println(fibonacci1(4));
+        System.out.println(fibonacci2(4,1,0));
+        System.out.println(fibonacciRe2(4, 1,1));
+        System.out.println(fibonacciDP(4));
+    }
+
+}