Create Solution.java

Author: Jerring

solution/0509.Fibonacci/Solution.java

@@ -0,0 +1,15 @@
+class Solution {
+    public int fib(int N) {
+        if (N < 2) {
+            return N;
+        }
+        int a = 0, b = 1;
+        int res = 0;
+        for (int i = 2; i <= N; ++i) {
+            res = a + b;
+            a = b;
+            b = res;
+        }
+        return res;
+    }
+}