题解 | #栈的压入、弹出序列#

class Stack {
    constructor(){
        this.item = []
    }
    
    push(i){
        this.item.push(i)
    }
    
    pop(){
        this.item.pop()
    }
    
    top(){
        return this.item[this.item.length - 1 ]
    }
    
    isEmpty(){
        return this.item.length === 0
    }
}

function IsPopOrder(pushV, popV)
{
    // write code here
    if(!pushV.length){
        return true
    }
    
    let stack = new Stack()
    let p = 0  //目前入栈到的下标  
    stack.push(pushV[p])  //初始化入栈1个
    
    for(let i = 0; i < popV.length; i++){
        while(stack.top() !== popV[i] ){  //继续入栈
            if(p === pushV.length - 1){    //已经全部入栈 无法入栈
                return false
            }
            stack.push(pushV[++p])
        }
        if(!stack.isEmpty() && stack.top() === popV[i] ){     //出栈
            stack.pop()            
        }
    }
    return true
}

module.exports = {
    IsPopOrder : IsPopOrder
};