LC 71. Simplify Path (Phython Stack)

Author: raul-sauco

README.md

@@ -73,7 +73,8 @@ Solutions to LeetCode problems. The first column links to the problem in LeetCod
 | [64. Minimum Path Sum][lc64]                                                                  | 🟠 Medium  | [![rust](res/rs.png)][lc64rs]                                                                         |
 | [66. Plus One][lc66]                                                                          | 🟢 Easy    | [![python](res/py.png)][lc66py]                                                                       |
 | [67. Add Binary][lc67]                                                                        | 🟢 Easy    | [![python](res/py.png)][lc67py] [![rust](res/rs.png)][lc67rs]                                         |
-| [70. Climbing Stairs][lc70]                                                                   | 🟢 Easy    | [![python](res/py.png)](leetcode/climbing-stairs.py)                                                  |
+| [70. Climbing Stairs][lc70]                                                                   | 🟢 Easy    | [![python](res/py.png)][lc70py]                                                                       |
+| [71. Simplify Path][lc71]                                                                     | 🟠 Medium  | [![python](res/py.png)][lc71py]                                                                       |
 | [72. Edit Distance][lc72]                                                                     | 🔴 Hard    | [![python](res/py.png)][lc72py] [![rust](res/rs.png)][lc72rs]                                         |
 | [73. Set Matrix Zeroes][lc73]                                                                 | 🟠 Medium  | [![python](res/py.png)][lc73py]                                                                       |
 | [74. Search a 2D Matrix][lc74]                                                                | 🟠 Medium  | [![python](res/py.png)][lc74py]                                                                       |
@@ -595,6 +596,9 @@ Solutions to LeetCode problems. The first column links to the problem in LeetCod
 [lc67py]: leetcode/add-binary.py
 [lc67rs]: leetcode/add-binary.rs
 [lc70]: https://leetcode.com/problems/climbing-stairs/
+[lc70py]: leetcode/climbing-stairs.py
+[lc71]: https://leetcode.com/problems/simplify-path/
+[lc71py]: leetcode/simplify-path.py
 [lc72]: https://leetcode.com/problems/edit-distance/
 [lc72py]: leetcode/edit-distance.py
 [lc72rs]: leetcode/edit-distance.rs

leetcode/simplify-path.py

@@ -0,0 +1,78 @@
+# 71. Simplify Path
+# 🟠 Medium
+#
+# https://leetcode.com/problems/simplify-path/
+#
+# Tags: String - Stack
+
+import re
+import timeit
+
+
+# First merge contiguous directory separators into one, then split by
+# directory separators. Iterate over the resulting directories or ".."
+# elements, when we see "." we don't do anything, when we see a ".." we
+# "travel" one directory up by popping the last element on the stack,
+# anything else we consider a directory name and we push into the stack.
+#
+# Time complexity: O(n) - Cleaning and tokenizing the input needs to
+# visit each character of the input path.
+# Space complexity: O(n) - The stack can have as many characters as the
+# input.
+#
+# Runtime 35 ms Beats 58.39%
+# Memory 13.8 MB Beats 69.41%
+class Solution:
+    def simplifyPath(self, path: str) -> str:
+        # Step 1 combine multiple '////' into '/'
+        clean = re.sub(r"/+", "/", path)
+        # Step 2 split into directory names.
+        # https://stackoverflow.com/a/34844548/2557030
+        tokens = [token for token in clean.split("/") if token]
+        # Use a stack to store directory names
+        stack = []
+        for token in tokens:
+            if token == ".":
+                continue
+            if token == "..":
+                if stack:
+                    stack.pop()
+                continue
+            stack.append(token)
+        return "/" + "/".join(stack)
+
+
+def test():
+    executors = [Solution]
+    tests = [
+        ["/../", "/"],
+        ["/a/..", "/"],
+        ["/a/../", "/"],
+        ["/home/", "/home"],
+        ["/abc/...", "/abc/..."],
+        ["/a/./b/../../c/", "/c"],
+        ["/a/../.././../../", "/"],
+        ["/../../../../../a", "/a"],
+        ["/home//foo/", "/home/foo"],
+        ["/a//b//c//////d", "/a/b/c/d"],
+        ["/a/./b/./c/./d/", "/a/b/c/d"],
+    ]
+    for executor in executors:
+        start = timeit.default_timer()
+        for _ in range(1):
+            for col, t in enumerate(tests):
+                sol = executor()
+                result = sol.simplifyPath(t[0])
+                exp = t[1]
+                assert result == exp, (
+                    f"\033[93m» {result} <> {exp}\033[91m for"
+                    + f" test {col} using \033[1m{executor.__name__}"
+                )
+        stop = timeit.default_timer()
+        used = str(round(stop - start, 5))
+        cols = "{0:20}{1:10}{2:10}"
+        res = cols.format(executor.__name__, used, "seconds")
+        print(f"\033[92m» {res}\033[0m")
+
+
+test()