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. */    vector<int> st;    int min=INT_MAX;    MinStack() {    }    void push(int x) {        if(x<min) min=x;        st.push_back(x);    }    void pop() {        if(st.back()==min)        {            st.pop_back();            int temp_min=INT_MAX;            for(vector<int>::iterator it=st.begin();it!=st.end();it++)            {                if(*it<temp_min) temp_min=*it;            }            min=temp_min;        }        else            st.pop_back();    }    int top() {        return st.back();    }    int getMin() {        return min;    }};/** * 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(); */