- Easy peasy

_015_climbingStairs.js

@@ -0,0 +1,31 @@
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var climbStairs = function(n, seenMap = {}) {
+    if (n === 0 || n === 1 || n === 2) return n;
+
+    let prev1 = n - 1;
+    let prev2 = n - 2;
+
+    let val1 = 0;
+    let val2 = 0;
+
+    if (prev1 in seenMap) {
+        val1 = seenMap[prev1];
+    } else {
+        val1 = climbStairs(prev1, seenMap);
+        seenMap[prev1] = val1;
+    }
+
+    if (prev2 in seenMap) {
+        val2 = seenMap[prev2];
+    } else {
+        val2 = climbStairs(prev2, seenMap);
+        seenMap[prev2] = val2;
+    }
+
+    seenMap[n] = val1 + val2;
+
+    return seenMap[n];
+};