155.最小栈.rs

/*
 * @lc app=leetcode.cn id=155 lang=rust
 *
 * [155] 最小栈
 *
 * https://leetcode-cn.com/problems/min-stack/description/
 *
 * algorithms
 * Easy (57.37%)
 * Likes:    1055
 * Dislikes: 0
 * Total Accepted:    295.5K
 * Total Submissions: 514.9K
 * Testcase Example:  '["MinStack","push","push","push","getMin","pop","top","getMin"]\n' +
  '[[],[-2],[0],[-3],[],[],[],[]]'
 *
 * 设计一个支持 push ，pop ，top 操作，并能在常数时间内检索到最小元素的栈。
 * 
 * 
 * push(x) —— 将元素 x 推入栈中。
 * pop() —— 删除栈顶的元素。
 * top() —— 获取栈顶元素。
 * getMin() —— 检索栈中的最小元素。
 * 
 * 
 * 
 * 
 * 示例:
 * 
 * 输入：
 * ["MinStack","push","push","push","getMin","pop","top","getMin"]
 * [[],[-2],[0],[-3],[],[],[],[]]
 * 
 * 输出：
 * [null,null,null,null,-3,null,0,-2]
 * 
 * 解释：
 * MinStack minStack = new MinStack();
 * minStack.push(-2);
 * minStack.push(0);
 * minStack.push(-3);
 * minStack.getMin();   --> 返回 -3.
 * minStack.pop();
 * minStack.top();      --> 返回 0.
 * minStack.getMin();   --> 返回 -2.
 * 
 * 
 * 
 * 
 * 提示：
 * 
 * 
 * pop、top 和 getMin 操作总是在 非空栈 上调用。
 * 
 * 
 */

// @lc code=start
struct MinStack {
    stack: Vec<i32>,
    min_stack: Vec<i32>,
}


/**
 * `&self` means the method takes an immutable reference.
 * If you need a mutable reference, change it to `&mut self` instead.
 */
impl MinStack {

    fn new() -> Self {
        MinStack {
            stack: Vec::new(),
            min_stack: Vec::new(),
        }
    }
    
    fn push(&mut self, val: i32) {
        self.stack.push(val);
        if self.min_stack.is_empty() || val <= *self.min_stack.last().unwrap() {
            self.min_stack.push(val);
        }
    }
    
    fn pop(&mut self) {
        if self.min_stack.is_empty() {
            return;
        }
        if self.stack.pop().unwrap() == *self.min_stack.last().unwrap() {
            self.min_stack.pop();
        }
    }
    
    fn top(&self) -> i32 {
        return *self.stack.last().unwrap();
    }
    
    fn get_min(&self) -> i32 {
        return *self.min_stack.last().unwrap();
    }
}

/**
 * Your MinStack object will be instantiated and called as such:
 * let obj = MinStack::new();
 * obj.push(val);
 * obj.pop();
 * let ret_3: i32 = obj.top();
 * let ret_4: i32 = obj.get_min();
 */
// @lc code=end