[JavaScript知识库]LeetCode-面试题 03.02. 栈的最小值_JavaScript

• 请设计一个栈，除了常规栈支持的pop与push函数以外，还支持min函数，该函数返回栈元素中的最小值。执行push、pop和min操作的时间复杂度必须为O(1)。

示例：

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.

程序代码

/**
 * initialize your data structure here.
 */
var MinStack = function() {
  this.item=[];
  this.help=[Infinity];
};

/** 
 * @param {number} x
 * @return {void}
 */
MinStack.prototype.push = function(x) {
 this.item.push(x);
 this.help.push(Math.min(x,this.help[this.help.length-1]))
};

/**
 * @return {void}
 */
MinStack.prototype.pop = function() {
 this.item.pop();
 this.help.pop();
};

/**
 * @return {number}
 */
MinStack.prototype.top = function() {
  return this.item[this.item.length-1]
};

/**
 * @return {number}
 */
MinStack.prototype.getMin = function() {
  return this.help[this.help.length-1]
};

/**
 * Your MinStack object will be instantiated and called as such:
 * var obj = new MinStack()
 * obj.push(x)
 * obj.pop()
 * var param_3 = obj.top()
 * var param_4 = obj.getMin()
 */