MinStack.h

Author: applewjg

MinStack.h

@@ -0,0 +1,44 @@
+/*
+ Author:     King, [email protected]
+ Date:       Nov 14, 2014
+ Problem:    Min Stack 
+ Difficulty: Easy
+ Source:     https://oj.leetcode.com/problems/min-stack/
+ Notes:
+ Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
+    push(x) -- Push element x onto stack.
+    pop() -- Removes the element on top of the stack.
+    top() -- Get the top element.
+    getMin() -- Retrieve the minimum element in the stack.
+*/
+
+class MinStack {
+public:
+    void push(int x) {
+        elements.push(x);
+        if (minstk.empty() || x <= minstk.top()) {
+            minstk.push(x);
+        }
+    }
+
+    void pop() {
+        if (elements.empty()) { 
+            return;
+        }
+        if (elements.top() == minstk.top()) {
+            minstk.pop();
+        }
+        elements.pop();
+    }
+
+    int top() {
+        return elements.top();
+    }
+
+    int getMin() {
+        return minstk.top();
+    }
+private:
+    stack<int> elements;
+    stack<int> minstk;
+};