From d6902d7c66fa896cb6ace542a150900af4e92e9d Mon Sep 17 00:00:00 2001
From: Lam Haoyin <root@eatswap.org>
Date: Mon, 14 Feb 2022 09:03:24 +0800
Subject: [PATCH] add: 220214-CN

---
 2202/220214-CN.cpp  | 35 +++++++++++++++++++++++++++++++++++
 2202/CMakeLists.txt |  2 +-
 2 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 2202/220214-CN.cpp

diff --git a/2202/220214-CN.cpp b/2202/220214-CN.cpp
new file mode 100644
index 0000000..b1bedd0
--- /dev/null
+++ b/2202/220214-CN.cpp
@@ -0,0 +1,35 @@
+#include <vector>
+#include <cstdio>
+
+/**
+ * 540. Single Element in a Sorted Array
+ * You are given a sorted array consisting of only integers where every element appears exactly twice, except for one element which appears exactly once.
+ * Return the single element that appears only once.
+ * Your solution must run in O(log n) time and O(1) space.
+ */
+
+class Solution {
+public:
+	static int singleNonDuplicate(const std::vector<int>& nums) {
+		int L = 0, R = nums.size();
+		if (R == 1)
+			return nums[0];
+
+		// Interval [L, R)
+		while (R - L > 1) {
+			int M = (L + R) >> 1;
+			if (nums[M] == nums[M ^ 1]) {
+				L = 1 + (M | 1);
+			} else {
+				R = (M & (~1)) + 1;
+			}
+		}
+
+		return nums[L];
+	}
+};
+
+int main() {
+	std::printf("%d\n", Solution::singleNonDuplicate({1,1,2,3,3}));
+	return 0;
+}
diff --git a/2202/CMakeLists.txt b/2202/CMakeLists.txt
index beda610..faaa539 100644
--- a/2202/CMakeLists.txt
+++ b/2202/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2202)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2202 220213.cpp)
+ADD_EXECUTABLE(2202 220214-CN.cpp)