js实现栈结构

实现栈结构

//创建栈
function Stack (){
    let items = []

    this.push = function(element){
        items.push(element)
    }
    this.pop = function(){
       return items.pop()
    }
    this.peek = function(){
        return items[items.length - 1]
    }
    this.isEmpty = function(){
        return items.length === 0
    }
    this.size = function(){
        return items.length
    }
    this.clear = function(){
        items = []
    }
    this.print = function(){
        console.log(items.toString())
    }
}

ES6改造

//使用Symbol添加私有属性
class Stack {
    let _items = Symbol()
    constructor(){
        this[_items] = []
    }
    push(element){
        this[_items].push(element)
    }
}

//可以拿到所有的symbol对象
Object.getOwnPropertySymbols(Stack)

//使用weakMap
const items = new weakMap()

class Stack {
    constructor(){
        items.set(this,[])
    }
    push(element){
        let s = items.get(this)
        s.push(element)
    }
    pop(){
        let s = items.get(this)
        let r = s.pop()
        return r
    }
}

//利用闭包实现私有属性
let Stack = (function(){
   const items = new WeackMap()

   class Stack {
    constructor(){
        items.set(this,[])
    }
    push(element){
        let s = items.get(this)
        s.push(element)
    }
    pop(){
        let s = items.get(this)
        let r = s.pop()
        return r
    }
}
   return Stack
})()

进制转换

//10进制转2进制
function divideBy2(decNumber){
    var remStack = new Stack(),
    rem,
    binaryString = '';

    while(decNumber > 0){
        rem = Math.floor(decNumber % 2)
        remStack.push(rem)
        decNumber = Math.floor(decNumber / 2)
    }

    while(!remStack.isEmpty()){
        binaryString += remStack.pop().toString()
    }
}

//任意进制转换
function baseConverter(decNumber,base){
  const remStack = new Stack();
  const digits = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
  let number = decNumber;
  let rem;
  let baseString = '';

  if (!(base >= 2 && base <= 36)) {
    return '';
  }

  while (number > 0) {
    rem = Math.floor(number % base);
    remStack.push(rem);
    number = Math.floor(number / base);
  }

  while (!remStack.isEmpty()) {
    baseString += digits[remStack.pop()];
  }

  return baseString;
}

平衡圆括号

function balancedSymbols(symbols){
    const stack =  new Stack()
    const opens = `([{`
    const closers = `)]}`

    let balanced = true
    let index = 0
    let symbol
    let top

    while(index < symbols.length && balanced){
        symbol = symbols[index]

        if(opens.indexOf(symbol) >= 0){
            stack.push(symbol)
        } else if(stack.isEmpty()){
            balanced = false
        } else {
            top = stack.pop()
            if(!(opens.indexOf(top) === closers.indexOf(symbol))){
                balanced = false
            }
        }

        index ++
    }
    return balanced && stack.isEmpty()
}

汉诺塔

递归，即定义一组基本操作，这组操作将规模小一点（或大一点）的操作当做一个整体——无需关心它的细节，只当它已经完成了——然后执行剩下的操作。而在更小或更大的规模中也依此操作，直到规模达到预定值。

function towerOfHanoi(plates,source,helper,dest,sourceName,helperName,destName,moves = []){
    if(plates <= 0){
        return moves
    }
    if(plates === 1){
        dest.push(source.pop())
        const move = {}
        move[sourceName] = source.toString()
        move[helperName] = helper.toString()
        move[destName] = dest.toString()
        moves.push(move)
    }
    else {
        towerOfHanoi(
            plates - 1,
            source,
            dest,
            helper,
            sourceName,
            destName,
            helperName,
            moves
        )
        dest.push(source.pop())
        const move = {}
        move[sourceName] = source.toString()
        move[helperName] = helper.toString()
        move[destName] = dest.toString()
        moves.push(move)
        towerOfHanoi(
            plates - 1,
            helper,
            source,
            dest,
            helperName,
            sourceName,
            destName,
            moves
        )
    }
    return moves
}

function hanoiStack(plates){
    const source = new Stack()
    const dest = new Stack()
    const helper = new Stack()

    for(let i = plates; i > 0; i --){
        source.push(i)
    }

    return towerOfHanoi(
        plates,
        source,
        helper,
        dest,
        source,
        helper,
        dest
    )
}

function hanoi(plates,source,helper,dest,moves = []){
    if(plates <= 0){
        return moves
    }
    if(plates === 1){
        moves.push([source,dest])
    } else {
        hanoi(
            plates - 1,
            source,
            dest,
            helper,
            moves
        )
        moves.push([source,dest])
    }
    return moves
}
//用栈来实现汉诺塔
console.log(hanoiStack(3));
//用递归来来实现
console.log(hanoi(3, 'source', 'helper', 'dest'));