From fbf88bd6e6d362b218502226adce6ef716fac11b Mon Sep 17 00:00:00 2001
From: Lam Haoyin <root@eatswap.org>
Date: Fri, 1 Apr 2022 00:38:22 +0800
Subject: [PATCH] add: start of April 2022!

---
 cpp/2204/220401-CN.cpp  | 34 ++++++++++++++++++++++++++++++++++
 cpp/2204/CMakeLists.txt |  6 ++++++
 cpp/CMakeLists.txt      |  3 ++-
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 cpp/2204/220401-CN.cpp
 create mode 100644 cpp/2204/CMakeLists.txt

diff --git a/cpp/2204/220401-CN.cpp b/cpp/2204/220401-CN.cpp
new file mode 100644
index 0000000..f0219d2
--- /dev/null
+++ b/cpp/2204/220401-CN.cpp
@@ -0,0 +1,34 @@
+#include <vector>
+#include <map>
+#include <iostream>
+
+/**
+ * 954. Array of Doubled Pairs
+ * Given an integer array of even length arr, return true if it is possible to reorder arr such that arr[2 * i + 1] = 2 * arr[2 * i] for every 0 <= i < len(arr) / 2, or false otherwise.
+ */
+
+class Solution {
+public:
+	static bool canReorderDoubled(const std::vector<int>& arr) {
+		std::map<int, int> s[2];
+		for (int i : arr)
+			++s[i >= 0][std::abs(i)];
+		for (std::map<int, int>& m : s) {
+			while (!m.empty()) {
+				int n = m.begin()->first;
+				if (!--m[n])
+					m.erase(n);
+				if (!m.count(2 * n))
+					return false;
+				if (!--m[2 * n])
+					m.erase(2 * n);
+			}
+		}
+		return true;
+	}
+};
+
+int main() {
+	std::cout << Solution::canReorderDoubled({2,4,0,0,8,1});
+	return 0;
+}
diff --git a/cpp/2204/CMakeLists.txt b/cpp/2204/CMakeLists.txt
new file mode 100644
index 0000000..1610c1f
--- /dev/null
+++ b/cpp/2204/CMakeLists.txt
@@ -0,0 +1,6 @@
+CMAKE_MINIMUM_REQUIRED(VERSION 3.21)
+PROJECT(2204)
+
+SET(CMAKE_CXX_STANDARD 23)
+
+ADD_EXECUTABLE(2204 220401-CN.cpp)
diff --git a/cpp/CMakeLists.txt b/cpp/CMakeLists.txt
index a674ca3..a2ee3f6 100644
--- a/cpp/CMakeLists.txt
+++ b/cpp/CMakeLists.txt
@@ -11,5 +11,6 @@ ADD_EXECUTABLE(leetcode-cpp main.cpp)
 # ADD_SUBDIRECTORY(2112)
 # ADD_SUBDIRECTORY(2201)
 # ADD_SUBDIRECTORY(2202)
-ADD_SUBDIRECTORY(2203)
+# ADD_SUBDIRECTORY(2203)
+ADD_SUBDIRECTORY(2204)
 ADD_SUBDIRECTORY(more)