add: 220418-CN [cpp]

cpp/2204/220418-CN.cpp

@@ -0,0 +1,55 @@
+#include <vector>
+#include <string>
+#include <format>
+#include <unordered_set>
+#include <iostream>
+
+/**
+ * 386. Lexicographical Numbers
+ * Given an integer n, return all the numbers in the range [1, n] sorted in lexicographical order.
+ * You must write an algorithm that runs in O(n) time and uses O(1) extra space.
+ */
+
+class Solution {
+public:
+	static std::vector<int> lexicalOrder(int n) {
+		auto next = [n](int x) {
+			if (10 * x <= n)
+				return 10 * x;
+			int nx = 1 + x;
+			while (!(nx % 10))
+				nx /= 10;
+			while (nx > n)
+				nx = nx / 10 + 1;
+			while (!(nx % 10))
+				nx /= 10;
+			return nx;
+		};
+
+		std::vector<int> ret;
+		ret.reserve(n);
+
+		for (int i = 0, j = 1; i < n; ++i, j = next(j))
+			ret.push_back(j);
+
+		return ret;
+	}
+};
+
+int main() {
+	const int T = 14959;
+	auto r = Solution::lexicalOrder(T);
+	auto n = r.size();
+	std::unordered_set<int> s;
+	s.insert(1);
+	for (int i = 1; i < n; ++i) {
+		if (std::to_string(r[i - 1]) >= std::to_string(r[i]) || r[i] > T || s.contains(r[i])) {
+			std::cout << std::format("Conflict: {} and {} at position {}\n", r[i - 1], r[i], i);
+		}
+		s.insert(r[i]);
+	}
+	for (int i = 1; i <= n; ++i)
+		if (!s.contains(i))
+			std::cout << std::format("Missing: {}\n", i);
+	return 0;
+}

cpp/2204/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2204)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2204 220417-CN.cpp)
+ADD_EXECUTABLE(2204 220418-CN.cpp)