70 - Climbing stairs

Author: asumaran

70-climbing-stairs.js

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+/**
+ * @param {number} n
+ * @return {number}
+ */
+// n = 2
+// 1 + 1
+// 2
+
+// n = 3
+// 1 + 1 + 1
+// 1 + 2
+// 2 + 1
+
+// n = 4
+// 1 + 1 + 1 + 1
+// 1 + 2 + 1
+// 2 + 1 + 1
+// 1 + 1 + 2
+// 2 + 2
+
+// n = 5
+// 1 + 1 + 1 + 1 + 1
+// 1 + 1 + 1 + 2
+// 1 + 2 + 1 + 1
+// 1 + 1 + 2 + 1
+// 1 + 2 + 2
+// 2 + 1 + 1 + 1
+// 2 + 1 + 2
+// 2 + 2 + 1
+
+// r = (n-1) + (n-2)
+const cache = [];
+var climbStairs = function (n) {
+  if (cache[n]) {
+    return cache[n];
+  }
+
+  if (n <= 3) {
+    cache[n] = n;
+    return n;
+  }
+
+  cache[n] = climbStairs(n - 2) + climbStairs(n - 1);
+  return cache[n];
+};
+
+console.log(climbStairs(1));