add Easy_70_Climbing_Stairs

Author: zongyanqi

Easy_70_Climbing_Stairs.js

@@ -0,0 +1,46 @@
+/**
+ * https://leetcode.com/problems/climbing-stairs/#/description
+ *
+ * You are climbing a stair case. It takes n steps to reach to the top.
+ * Each time you can either climb 1 or 2 steps.
+ * In how many distinct ways can you climb to the top?
+ *
+ * Note: Given n will be a positive integer.
+ *
+ * 答案:
+ *
+ * https://leetcode.com/articles/climbing-stairs/
+ */
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var climbStairs = function (n) {
+    if (n < 2) return 1;
+    return climbStairs(n - 1) + climbStairs(n - 2);
+};
+
+/**
+ * @param {number} n
+ * @return {number}
+ */
+var climbStairs2 = function (n) {
+    var ways = [1, 1];
+    for (var i = 2; i <= n; i++) {
+        ways[i] = ways[i - 1] + ways[i - 2];
+    }
+    return ways[n];
+};
+
+console.log(climbStairs(1));
+console.log(climbStairs(2));
+console.log(climbStairs(3));
+console.log(climbStairs(4));
+
+console.log('==============');
+
+console.log(climbStairs2(1));
+console.log(climbStairs2(2));
+console.log(climbStairs2(3));
+console.log(climbStairs2(4));