Add solution #70

Author: JoshCrozier

README.md

@@ -53,6 +53,7 @@
 58|[Length of Last Word](./0058-length-of-last-word.js)|Easy|
 66|[Plus One](./0066-plus-one.js)|Easy|
 67|[Add Binary](./0067-add-binary.js)|Easy|
+70|[Climbing Stairs](./0070-climbing-stairs.js)|Easy|
 73|[Set Matrix Zeroes](./0073-set-matrix-zeroes.js)|Medium|
 74|[Search a 2D Matrix](./0074-search-a-2d-matrix.js)|Medium|
 77|[Combinations](./0077-combinations.js)|Medium|

solutions/0070-climbing-stairs.js

@@ -0,0 +1,26 @@
+/**
+ * 70. Climbing Stairs
+ * https://leetcode.com/problems/climbing-stairs/
+ * Difficulty: Easy
+ *
+ * You are climbing a staircase. It takes n steps to reach the top.
+ *
+ * Each time you can either climb 1 or 2 steps. In how many distinct
+ * ways can you climb to the top?
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var climbStairs = function(n) {
+  const cache = new Map();
+  const memo = n => {
+    if (n < 4) return n;
+    if (!cache.has(n)) {
+      cache.set(n, memo(n - 2) + memo(n - 1));
+    }
+    return cache.get(n);
+  };
+  return memo(n);
+};