leetcode Min Stack

原题链接：https://leetcode.com/problems/min-stack/

Description

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) {
if (val.empty() || x <= val.top()) val.push(x);
num.push(x);
}
void pop() {
if (num.top() <= val.top()) val.pop();
num.pop();
}
int top() {
return num.top();
}
int getMin() {
return val.top();
}
private:
stack<int> num;
stack<int> val;
};