155.min-stack.cpp

/*
 * @lc app=leetcode id=155 lang=cpp
 *
 * [155] Min Stack
 *
 * https://leetcode.com/problems/min-stack/description/
 *
 * algorithms
 * Easy (45.89%)
 * Likes:    4683
 * Dislikes: 431
 * Total Accepted:    685.1K
 * Total Submissions: 1.5M
 * Testcase Example:  '["MinStack","push","push","push","getMin","pop","top","getMin"]\n[[],[-2],[0],[-3],[],[],[],[]]'
 *
 * 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 1:
 * 
 * 
 * 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
 * 
 * 
 * 
 * Constraints:
 * 
 * 
 * Methods pop, top and getMin operations will always be called on non-empty
 * stacks.
 * 
 * 
 */

// @lc code=start
class MinStack {
public:
    /** initialize your data structure here. */
    MinStack() {
        
    }
    
    void push(int x) {
        comSt.push(x);
        if (!minSt.empty() && minSt.top() < x)
            minSt.push(minSt.top());
        else 
            minSt.push(x);
    }
    
    void pop() {
        comSt.pop();
        minSt.pop();
    }
    
    int top() {
        return comSt.top();
    }
    
    int getMin() {
        return minSt.top();
    }
private:
    stack<int> comSt;
    stack<int> minSt;
};

/**
 * 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();
 */
// @lc code=end