climbing-stairs

Author: taewanseoul

climbing-stairs/taewanseoul.ts

@@ -0,0 +1,26 @@
+/**
+ * 70. Climbing Stairs
+ * 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?
+ *
+ * https://leetcode.com/problems/climbing-stairs/description/
+ */
+function climbStairs(n: number): number {
+  if (n <= 2) {
+    return n;
+  }
+
+  let prev = 1;
+  let cur = 2;
+
+  for (let i = 3; i < n + 1; i++) {
+    const next = prev + cur;
+    prev = cur;
+    cur = next;
+  }
+
+  return cur;
+}
+
+// O(n) time
+// O(1) space