LC 119. Pascal's Triangle II (Python DP)

Author: raul-sauco

README.md

@@ -113,7 +113,7 @@ Solutions to LeetCode problems. The first column links to the problem in LeetCod
 | [114. Flatten Binary Tree to Linked List][lc114]                                              | 🟠 Medium  | [![python](res/py.png)][lc114py]                                                                      |
 | [115. Distinct Subsequences][lc115]                                                           | 🔴 Hard    | [![python](res/py.png)][lc115py]                                                                      |
 | [118. Pascal's Triangle][lc118]                                                               | 🟢 Easy    | [![python](res/py.png)][lc118py] [![rust](res/rs.png)][lc118rs]                                       |
-| [119. Pascal's Triangle II][lc119]                                                            | 🟢 Easy    | [![rust](res/rs.png)][lc119rs]                                                                        |
+| [119. Pascal's Triangle II][lc119]                                                            | 🟢 Easy    | [![python](res/py.png)][lc119py] [![rust](res/rs.png)][lc119rs]                                       |
 | [120. Triangle][lc120]                                                                        | 🟠 Medium  | [![python](res/py.png)][lc120py]                                                                      |
 | [121. Best Time to Buy and Sell Stock][lc121]                                                 | 🟢 Easy    | [![python](res/py.png)][lc121py] [![rust](res/rs.png)][lc121rs]                                       |
 | [124. Binary Tree Maximum Path Sum][lc124]                                                    | 🔴 Hard    | [![python](res/py.png)][lc124py]                                                                      |
@@ -827,6 +827,7 @@ Solutions to LeetCode problems. The first column links to the problem in LeetCod
 [lc118py]: leetcode/pascals-triangle.py
 [lc118rs]: leetcode/pascals-triangle.rs
 [lc119]: https://leetcode.com/problems/pascals-triangle-ii/
+[lc119py]: leetcode/pascals-triangle-ii.py
 [lc119rs]: leetcode/pascals-triangle-ii.rs
 [lc120]: https://leetcode.com/problems/triangle/
 [lc120py]: leetcode/triangle.py

leetcode/pascals-triangle-ii.py

@@ -0,0 +1,58 @@
+# 119. Pascal's Triangle II
+# 🟢 Easy
+#
+# https://leetcode.com/problems/pascals-triangle-ii/
+#
+# Tags: Array - Dynamic Programming
+
+import timeit
+from typing import List
+
+
+# Iterate over n number of rows, for each row, iterate over the row
+# elements backwards computing their new value as the sum of the element
+# at the same position plus the one at the previous position on the
+# previous row.
+#
+# Time complexity: O(n^2) - We iterate n rows, for each row, we iterate
+# over all the row elements.
+# Space complexity: O(n) - We use an extra array of size n.
+#
+# Runtime 35 ms Beats 77.91%
+# Memory 16.04 MB Beats 96.64%
+class Solution:
+    def getRow(self, rowIndex: int) -> List[int]:
+        row = [0] * (rowIndex + 1)
+        row[0] = 1
+        for i in range(1, rowIndex + 1):
+            for j in range(i, 0, -1):
+                row[j] += row[j - 1]
+        return row
+
+
+def test():
+    executors = [Solution]
+    tests = [
+        [0, [1]],
+        [1, [1, 1]],
+        [3, [1, 3, 3, 1]],
+    ]
+    for executor in executors:
+        start = timeit.default_timer()
+        for _ in range(1):
+            for col, t in enumerate(tests):
+                sol = executor()
+                result = sol.getRow(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()