leetcode_num155_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.

• class MinStack {
  public:
      void push(int x) {
          stack1.push(x);
          if(stack2.empty())
              stack2.push(x);
          else{
              int tmp=stack2.top();
              if(x>tmp)
                  stack2.push(tmp);
              else
                  stack2.push(x);
          }
      }
  
      void pop() {
          if((!stack1.empty())&&(!stack2.empty())){
              stack1.pop();
              stack2.pop();
          }
          else
              cout<<"EMPTY!"<<endl;
  
      }
  
      int top() {
          if(!stack1.empty())
              return stack1.top();
      }
  
      int getMin() {
          if(!stack2.empty())
              return stack2.top();
  
      }
  private:
      stack<int> stack1;
      stack<int> stack2;
  };