climbing stairs

Author: hjeomdev

climbing-stairs/hjeomdev.java

@@ -0,0 +1,18 @@
+class Solution {
+    List<Integer> list = new ArrayList<>();
+    public int climbStairs(int n) {
+        list.add(0);
+        list.add(1);
+        list.add(2);
+        return step(n);
+    }
+
+    public int step(int n) {
+        if (list.size() > n && list.get(n) != null) {
+            return list.get(n);
+        }
+        int result = step(n - 1) + step(n - 2);
+        list.add(result);
+        return result;
+    }
+}