climbing-stairs

Author: Hoonjichoi1

climbing-stairs/hoonjichoi1.java

@@ -0,0 +1,26 @@
+
+/*
+f(45) = f(44) + f(43)
+f(44) = f(43) + f(42)
+.
+.
+.
+f(3) = f(2) + f(1)
+f(2) = 2
+f(1) = 1
+*/
+class Solution {
+    public int climbStairs(int n) {
+        if (n <= 2) return n;
+
+        int prev = 1;
+        int result = 2;
+        int temp = 0;
+        for (int i = 2; i < n ; i++) {
+            temp = result;
+            result += prev;
+            prev = temp;
+        }     
+        return result;
+    }
+}