day 28: 155-min-stack, 150-evaluate-reverse-polish-notation

155-min-stack/driver.cpp

@@ -0,0 +1,14 @@
+#include "soln.hpp"
+
+int main()
+{
+	MinStack *minStack = new MinStack();
+	minStack->push(-2);
+	minStack->push(0);
+	minStack->push(-3);
+	cout << minStack->getMin() << endl; // return -3
+	minStack->pop();
+	cout << minStack->top() << endl;	// return 0
+	cout << minStack->getMin() << endl; // return -2
+	return 0;
+}

155-min-stack/soln.cpp

@@ -0,0 +1,32 @@
+#include "soln.hpp"
+
+MinStack::MinStack()
+{
+	_stack = {};
+	total_min = INT_MAX;
+}
+
+void MinStack::push(int val)
+{
+	total_min = min(int(val), total_min);
+	_stack.push_back({val, total_min});
+}
+
+void MinStack::pop()
+{
+	_stack.pop_back();
+	if (_stack.size() == 0)
+		total_min = INT_MAX;
+	else
+		total_min = _stack.back().second;
+}
+
+int MinStack::top()
+{
+	return int(_stack.back().first);
+}
+
+int MinStack::getMin()
+{
+	return int(_stack.back().second);
+}

155-min-stack/soln.hpp

@@ -0,0 +1,15 @@
+#include <bits/stdc++.h>
+using namespace std;
+class MinStack
+{
+private:
+	vector<pair<int, int>> _stack;
+	int total_min;
+
+public:
+	MinStack();
+	void push(int val);
+	void pop();
+	int top();
+	int getMin();
+};