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shuffle.js
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54 lines (45 loc) · 1.47 KB
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/**
* @description 洗牌算法
* @see https://github.com/mqyqingfeng/Blog/issues/51
**/
//旧版本的chrome对于10个元素内的数组使用插入算法进行排序(最新版已经修改了排序算法)
function originSort(arr) {
arr = arr.sort(() => Math.random() - 0.5)
return arr
}
//原理是将当前元素之后的所有元素中随机选取一个和当前元素互换
function shuffle(arr) {
for (let i = 0; i < arr.length; i++) {
let randomIndex = i + Math.floor(Math.random() * (arr.length - i));
[arr[i], arr[randomIndex]] = [arr[randomIndex], arr[i]]
}
return arr
}
//新生成一个数组,随机从原数组中取出一个元素放入新数组
function shuffle2(arr) {
let _arr = []
while (arr.length) {
let randomIndex = Math.floor(Math.random() * (arr.length))
_arr.push(arr.splice(randomIndex, 1)[0])
}
return _arr
}
// 分析概率的函数
function statistics(fn, arr) {
let times = 100000;
let res = {};
for (let i = 0; i < times; i++) {
//每次循环声明一次防止引用同一数组
let _arr = [...arr]
let key = JSON.stringify(fn(_arr));
res[key] ? res[key]++ : res[key] = 1;
}
// 为了方便展示，转换成百分比
Object.keys(res).forEach(key => {
res[key] = res[key] / times * 100 + '%'
})
console.log(fn.name,res)
}
statistics(originSort, [1, 2, 3])
statistics(shuffle, [1, 2, 3])
statistics(shuffle2, [1, 2, 3])