From a9cc05a3f384a711bbd7647c64d3d36b5566969b Mon Sep 17 00:00:00 2001
From: eat-swap <root@eatswap.org>
Date: Sat, 16 Apr 2022 22:09:51 +0800
Subject: [PATCH] add: 220416-CN [cpp]

---
 cpp/2204/220416-CN.cpp  | 49 +++++++++++++++++++++++++++++++++++++++++
 cpp/2204/220416.cpp     |  9 ++++++++
 cpp/2204/CMakeLists.txt |  2 +-
 3 files changed, 59 insertions(+), 1 deletion(-)
 create mode 100644 cpp/2204/220416-CN.cpp

diff --git a/cpp/2204/220416-CN.cpp b/cpp/2204/220416-CN.cpp
new file mode 100644
index 0000000..ad56113
--- /dev/null
+++ b/cpp/2204/220416-CN.cpp
@@ -0,0 +1,49 @@
+#include <cstdio>
+
+#define MIN(a, b) (((a) < (b)) ? (a) : (b))
+
+/**
+ * 479. Largest Palindrome Product
+ * Given an integer n, return the largest palindromic integer that can be represented as the product of two n-digits integers. Since the answer can be very large, return it modulo 1337.
+ */
+
+class Solution {
+private:
+	static inline constexpr unsigned long long get9(int n) {
+		unsigned long long ans = 0;
+		while (n--)
+			ans = ans * 10 + 9;
+		return ans;
+	}
+
+	static inline constexpr int getAns(int n) {
+		auto halfMax = get9(n), halfMin = 1 + get9(n - 1);
+		for (auto i = halfMax; i >= halfMin; --i) {
+			unsigned long long iFull = 0;
+			for (auto j = i; j; j /= 10) {
+				iFull = 10 * iFull + j % 10;
+			}
+			iFull += i * (1 + halfMax);
+			for (auto j = MIN(halfMax, iFull / halfMin); iFull / j <= halfMax && j >= halfMin; --j) {
+				if (iFull % j == 0) {
+					// std::printf("%llu %llu\n", iFull, j);
+					return iFull % 1337;
+				}
+			}
+		}
+		return 0;
+	}
+public:
+	static constexpr int largestPalindrome(int n) {
+		// const static int ans[] = {-1, 9, 987, 123, 597, 677, 1218, 877, 475};
+		// return ans[n];
+		return n == 1 ? 9 : getAns(n);
+	}
+};
+
+int main() {
+	for (int i = 2; i <= 8; ++i) {
+	//	std::printf("%d\n", getAns(i));
+	}
+	return 0;
+}
diff --git a/cpp/2204/220416.cpp b/cpp/2204/220416.cpp
index 3105e44..29aa6d1 100644
--- a/cpp/2204/220416.cpp
+++ b/cpp/2204/220416.cpp
@@ -7,6 +7,15 @@ struct TreeNode {
 	explicit TreeNode(int x, TreeNode* left = nullptr, TreeNode* right = nullptr) : val(x), left(left), right(right) {}
 };
 
+/**
+ * 538. Convert BST to Greater Tree
+ * Given the root of a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus the sum of all keys greater than the original key in BST.
+ * As a reminder, a binary search tree is a tree that satisfies these constraints:
+ * The left subtree of a node contains only nodes with keys less than the node's key.
+ * The right subtree of a node contains only nodes with keys greater than the node's key.
+ * Both the left and right subtrees must also be binary search trees.
+ */
+
 class Solution {
 public:
 	static TreeNode* convertBST(TreeNode* root) {
diff --git a/cpp/2204/CMakeLists.txt b/cpp/2204/CMakeLists.txt
index 39ae9f1..a6b2cab 100644
--- a/cpp/2204/CMakeLists.txt
+++ b/cpp/2204/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2204)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2204 220416.cpp)
+ADD_EXECUTABLE(2204 220416-CN.cpp)