add: 230310

cpp/2303/230310.cpp

@@ -0,0 +1,47 @@
+#include <cstdlib>
+#include <ctime>
+#include <vector>
+
+struct ListNode {
+	int val;
+	ListNode* next;
+
+	explicit ListNode(int x = 0, ListNode* next = nullptr) : val(x), next(next) {}
+};
+
+ListNode* construct(int x) {
+	return new ListNode(x);
+}
+
+template<typename... Ts>
+ListNode* construct(int x, Ts... xs) {
+	return new ListNode(x, construct(xs...));
+}
+
+/**
+ * 382. Linked List Random Node
+ * Given a singly linked list, return a random node's value from the linked list. Each node must have the same probability of being chosen.
+ *
+ * Implement the Solution class:
+ *
+ * Solution(ListNode head) Initializes the object with the head of the singly-linked list head.
+ * int getRandom() Chooses a node randomly from the list and returns its value. All the nodes of the list should be equally likely to be chosen.
+ */
+
+class Solution {
+private:
+	std::vector<short> s;
+
+public:
+	explicit Solution(ListNode* head) {
+		for (auto* ptr = head; ptr; ptr = ptr->next)
+			s.push_back(ptr->val);
+		std::srand(std::time(nullptr));
+	}
+
+	int getRandom() const {
+		int r = rand();
+		for (; r >= RAND_MAX / s.size() * s.size(); r = rand());
+		return s[r % s.size()];
+	}
+};

cpp/2303/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2303)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2303 230303.cpp)
+ADD_EXECUTABLE(2303 230310.cpp)