LeetCode 70. Climbing Stairs

Author: raul-sauco

README.md

@@ -20,6 +20,7 @@ Proposed solutions to some LeetCode problems. The first column links to the prob
 | [52. N-Queens II][lc52]                                                 | Hard       | [python](leetcode/n-queens-ii.py)                                             |
 | [53. Maximum Subarray][lc53]                                            | Easy       | [python](leetcode/maximum-subarray.py)                                        |
 | [55. Jump Game][lc55]                                                   | Medium     | [python](leetcode/jump-game.py)                                               |
+| [70. Climbing Stairs][lc70]                                             | Easy       | [python](leetcode/climbing-stairs.py)                                         |
 | [88. Merge Sorted Array][lc88]                                          | Easy       | [python](leetcode/merge-sorted-array.py)                                      |
 | [104. Maximum Depth of Binary Tree][lc104]                              | Easy       | [python](leetcode/maximum-depth-of-binary-tree.py)                            |
 | [120. Triangle][lc120]                                                  | Medium     | [python](leetcode/triangle.py)                                                |
@@ -103,6 +104,7 @@ First column is the problem difficulty, in descending order, second links to the
 [lc52]: https://leetcode.com/problems/n-queens-ii/
 [lc53]: https://leetcode.com/problems/maximum-subarray/
 [lc55]: https://leetcode.com/problems/jump-game/
+[lc70]: https://leetcode.com/problems/climbing-stairs/
 [lc88]: https://leetcode.com/problems/merge-sorted-array/
 [lc104]: https://leetcode.com/problems/maximum-depth-of-binary-tree/
 [lc120]: https://leetcode.com/problems/triangle/

leetcode/climbing-stairs.py

@@ -0,0 +1,53 @@
+# https://leetcode.com/problems/climbing-stairs/
+
+# Intuition, I can reach each step from n-1 and n-2, add the ways to reach them
+# It is a fibonacci sequence
+import timeit
+
+# Runtime: 42 ms, faster than 59.35% of Python3 online submissions for Climbing Stairs.
+# Memory Usage: 13.8 MB, less than 57.08 % of Python3 online submissions for Climbing Stairs.
+
+
+class Solution:
+    def climbStairs(self, n: int) -> int:
+        # Between 0 and 2, return the value itself
+        if n < 3:
+            return n
+        # Initialize pointers with the seeds
+        pp, p = 1, 1
+        # Iterate from 2 to n-1
+        for _ in range(n):
+            # Increase the values of the next table positions
+            # 0 1 2 3 5 8 13 ...
+            pp, p = p, p + pp
+        # Return the memoized value of adding up n-1 + n-2 up to n
+        return pp
+
+
+def test():
+    executors = [
+        {'executor': Solution, 'title': 'Solution', },
+    ]
+    tests = [
+        [0, 0],
+        [1, 1],
+        [2, 2],
+        [3, 3],
+        [5, 8],
+    ]
+    for executor in executors:
+        start = timeit.default_timer()
+        for _ in range(int(float('1'))):
+            for t in tests:
+                sol = executor['executor']()
+                result = sol.climbStairs(t[0])
+                expected = t[1]
+                assert result == expected, f'{result} != {expected}'
+        stop = timeit.default_timer()
+        used = str(round(stop - start, 5))
+        res = "{0:20}{1:10}{2:10}".format(
+            executor['title'], used, "seconds")
+        print(f"\033[92m» {res}\033[0m")
+
+
+test()