155. Min Stack

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

Implement the MinStack class:

• MinStack() initializes the stack object.
• void push(val) pushes the element val onto the stack.
• void pop() removes the element on the top of the stack.
• int top() gets the top element of the stack.
• int getMin() retrieves 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

class MinStack {
public:
    /** initialize your data structure here. */
    int t;
    vector<int> v;
    
    MinStack() {
        v.clear();
        t = -1;
    }
    
    void push(int val) {
        v.push_back(val);
        t++;
    }
    
    void pop() {
       v.pop_back();
       t--;   
    }
    
    int top() {
        return v[t];
    }
    
    int getMin() {
        return *min_element(v.begin(), v.end());
    }
};
/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack* obj = new MinStack();
 * obj->push(val);
 * obj->pop();
 * int param_3 = obj->top();
 * int param_4 = obj->getMin();
 */

使用vector，但超慢的LOL

Runtime: 100 ms, faster than 8.70% of C++ online submissions for Min Stack.

Memory Usage: 16.2 MB, less than 99.04% of C++ online submissions for Min Stack.