155. Min Stack

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.

Example:

MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin();   --> Returns -3.
minStack.pop();
minStack.top();      --> Returns 0.
minStack.getMin();   --> Returns -2.

class MinStack {
public:
    /** initialize your data structure here. */
    
    stack tempStack;
    stack minStack;
    
    
    void push(int x) {
        tempStack.push(x);
        if(minStack.empty()||x<=minStack.top())
          minStack.push(x);
    }
    
    void pop() {
        if(minStack.top()==tempStack.top())
        {
            tempStack.pop();
            minStack.pop();
        }
        else
           tempStack.pop();
    }
    
    int top() {
            return tempStack.top();
      
    }
    
    int getMin() {
            return minStack.top();
    }
};

/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack obj = new MinStack();
 * obj.push(x);
 * obj.pop();
 * int param_3 = obj.top();
 * int param_4 = obj.getMin();
 */