Min Stack

 

 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.

Input
["MinStack","push","push","push","getMin","pop","top","getMin"]
[[],[-2],[0],[-3],[],[],[],[]]

Output
[null,null,null,null,-3,null,0,-2]

Explanation
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin(); // return -3
minStack.pop();
minStack.top();    // return 0
minStack.getMin(); // return -2 

class MinStack {
     vector<int> s;
      int mn;
public:
    /** initialize your data structure here. */
   
    MinStack() {
           mn=INT_MAX;
    }
    
    void push(int x) {
        s.push_back(x);
        if(x<mn)
          mn=x;
            
    }
    
    void pop() {
        
            if(s.back()==mn)
            {
                 mn=INT_MAX;
                for(int i=0;i<s.size()-1;++i)
                {
                    if(s[i]<mn)
                        mn=s[i];
                }
            }
            
            s.pop_back();           
    }
    
    int top() {
        if(!s.empty())
        {
            return s.back();
        }else{
            return -1;
        }
    }
    
    int getMin() {
        return mn;
        
    }
};