From c18f7f47bf7313287bcc98620d32c6d181557114 Mon Sep 17 00:00:00 2001
From: Lam Haoyin <root@eatswap.org>
Date: Sat, 19 Mar 2022 14:43:29 +0800
Subject: [PATCH] add: 220319 [cpp]

---
 cpp/2203/220319.cpp     | 98 +++++++++++++++++++++++++++++++++++++++++
 cpp/2203/CMakeLists.txt |  2 +-
 2 files changed, 99 insertions(+), 1 deletion(-)
 create mode 100644 cpp/2203/220319.cpp

diff --git a/cpp/2203/220319.cpp b/cpp/2203/220319.cpp
new file mode 100644
index 0000000..6580690
--- /dev/null
+++ b/cpp/2203/220319.cpp
@@ -0,0 +1,98 @@
+#include <list>
+#include <unordered_map>
+#include <unordered_set>
+#include <map>
+#include <algorithm>
+#include <iostream>
+#include <queue>
+#include <stack>
+
+class FreqStack {
+private:
+	std::unordered_map<int, std::stack<int>> s;
+	std::unordered_map<int, int> val2Freq;
+	int maxFreq = 0;
+public:
+	FreqStack() = default;
+
+	void push(int val) {
+		int newFreq = ++val2Freq[val];
+		maxFreq = std::max(maxFreq, newFreq);
+		s[newFreq].push(val);
+	}
+
+	int pop() {
+		int ret = s[maxFreq].top();
+		s[maxFreq].pop();
+		if (s[maxFreq].empty()) {
+			--maxFreq;
+		}
+		--val2Freq[ret];
+		return ret;
+	}
+};
+
+class FreqStackOld {
+private:
+	std::list<int> stack;
+	std::map<int, std::unordered_set<int>> freq2Val;
+	std::unordered_map<int, int> val2Freq;
+public:
+	FreqStackOld() = default;
+
+	void push(int val) {
+		int newFreq = ++val2Freq[val];
+		stack.push_front(val);
+		if (newFreq > 1) {
+			if (freq2Val[newFreq - 1].size() <= 1)
+				freq2Val.erase(newFreq - 1);
+			else
+				freq2Val[newFreq - 1].erase(val);
+		}
+		freq2Val[newFreq].insert(val);
+	}
+
+	int pop() {
+		// Get most frequent element
+		std::unordered_set<int>& s = freq2Val.rbegin()->second;
+		std::list<int>::iterator toErase;
+		if (s.size() == 1) {
+			toErase = std::find(stack.begin(), stack.end(), *s.begin());
+			freq2Val.erase(std::prev(freq2Val.end()));
+		} else {
+			toErase = stack.begin();
+			for (auto it = stack.begin(); it != stack.end(); ++it) {
+				bool OK = false;
+				for (int i: s) {
+					if (*it == i) {
+						// Found that, will erase;
+						toErase = it;
+						OK = true;
+						break;
+					}
+				}
+				if (OK) break;
+			}
+			freq2Val.rbegin()->second.erase(*toErase);
+		}
+		int newFreq = --val2Freq[*toErase], ret = *toErase;
+		freq2Val[newFreq].insert(*toErase);
+		stack.erase(toErase);
+		return ret;
+	}
+};
+
+int main() {
+	FreqStack freqStack;
+	freqStack.push(5); // The stack is [5]
+	freqStack.push(7); // The stack is [5,7]
+	freqStack.push(5); // The stack is [5,7,5]
+	freqStack.push(7); // The stack is [5,7,5,7]
+	freqStack.push(4); // The stack is [5,7,5,7,4]
+	freqStack.push(5); // The stack is [5,7,5,7,4,5]
+	std::cout << std::endl << freqStack.pop();   // return 5, as 5 is the most frequent. The stack becomes [5,7,5,7,4].
+	std::cout << std::endl << freqStack.pop();   // return 7, as 5 and 7 is the most frequent, but 7 is closest to the top. The stack becomes [5,7,5,4].
+	std::cout << std::endl << freqStack.pop();   // return 5, as 5 is the most frequent. The stack becomes [5,7,4].
+	std::cout << std::endl << freqStack.pop();   // return 4, as 4, 5 and 7 is the most frequent, but 4 is closest to the top. The stack becomes [5,7].
+	return 0;
+}
diff --git a/cpp/2203/CMakeLists.txt b/cpp/2203/CMakeLists.txt
index 2f517f8..09e998f 100644
--- a/cpp/2203/CMakeLists.txt
+++ b/cpp/2203/CMakeLists.txt
@@ -3,4 +3,4 @@ PROJECT(2203)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2203 220319-CN.cpp)
+ADD_EXECUTABLE(2203 220319.cpp)