Add leetcode 20 task solution

leetcode/dynamic_arrays/1929_concatenation_of_array.py

@@ -0,0 +1,17 @@
+# Link: https://leetcode.com/problems/concatenation-of-array/
+from typing import List
+
+
+class Solution:
+    def getConcatenation(self, nums: List[int]) -> List[int]:
+        # ans = [] * (len(nums) * 2)
+        ans = nums + nums
+        return ans
+
+
+if __name__ == "__main__":
+    nums = [2, 5, 1, 3, 4, 7]
+    sol = Solution
+    print(nums)
+    print(sol().getConcatenation(nums))
+    print("-" * 60)

leetcode/stacks/20_valid_parentheses.py

@@ -0,0 +1,58 @@
+# Link: https://leetcode.com/problems/valid-parentheses/description/
+
+
+class Solution:
+    def isValid(self, s: str) -> bool:
+        c = []  # Checker stack
+        m = {
+            ")": "(",
+            "}": "{",
+            "]": "[",
+        }
+        cb = m.keys()
+        op = m.values()
+        for char in s:
+            if len(c) == 0:
+                c.append(char)
+                continue
+            if char in op:
+                c.append(char)
+                continue
+            if char in cb:
+                if len(c) > 0 and c[-1] == m[char]:
+                    c.pop()
+                    continue
+                if len(c) > 0 and c[-1] != m[char]:
+                    return False
+                if len(c) == 0:
+                    return False
+        print(f"c = {c} (len={len(c)})")
+        return False if len(c) > 0 else True
+
+
+if __name__ == "__main__":
+    tt = "()[]{}"
+    sol = Solution
+    print(f"Initial: {tt}")
+    print(sol().isValid(tt))
+    print("-" * 60)
+    tt = "()"
+    print(f"Initial: {tt}")
+    print(sol().isValid(tt))
+    print("-" * 60)
+    tt = "())"
+    print(f"Initial: {tt}")
+    print(sol().isValid(tt))
+    print("-" * 60)
+    tt = "([])"
+    print(f"Initial: {tt}")
+    print(sol().isValid(tt))
+    print("-" * 60)
+    tt = "("
+    print(f"Initial: {tt}")
+    print(sol().isValid(tt))
+    print("-" * 60)
+    tt = "(])"
+    print(f"Initial: {tt}")
+    print(sol().isValid(tt))
+    print("-" * 60)