1. // 假设本地机器无法做加减乘除法，需要通过远程请求让服务端来实现。
    2.         // 以加法为例，现有远程API的模拟实现
    3.         const addRemote = async (a, b) => new Promise(resolve => {
    4.             setTimeout(() => resolve(a + b), 1000)
    5.         })
    6.         let starttime = new Date().getTime()
    7.         // 请实现本地的add方法，调用addRemote，能最优的实现输入数字的加法。
    8.         const map = new Map()
    9.         const getMapKeys = (inputs) => {
    10.             let mapKeys = []
    11.             inputs = inputs.sort((a, b) => a - b)
    12.             for (let i = 0;i<inputs.length; i++) {
    13.                 if (inputs.length - i <= inputs.length/2) {
    14.                     mapKeys.push([`${inputs[i]}+${inputs[inputs.length -i]}`, `${inputs[inputs.length -i]}+${inputs[i]}`])
    15.                 }
    16.             }
    17.             return mapKeys
    18.         }
    19.         const caculate = async (key) => {
    20.             let agrs = key.split('+')
    21.             agrs = agrs.map(e=> +e)
    22.             return await addRemote(...agrs)
    23.         }
    24.         async function add(...inputs) {
    25.             // 你的实现
    26.             if (inputs.length <2) return inputs
    27.             let mapKeys = getMapKeys(inputs)
    28.             let res = 0;
    29.             for (let i = 0; i<mapKeys.length; i++) {
    30.                 // console.log('map', map)
    31.                 if (map.has(mapKeys[i][0])) {
    32.                     res += map.get(mapKeys[i][0])
    33.                 } else if(map.has(mapKeys[i][1])) {
    34.                     res += map.get(mapKeys[i][1])
    35.                 } else {
    36.                     let result = await caculate(mapKeys[i][0])
    37.                     map.set(mapKeys[i][0], result)
    38.                     map.set(mapKeys[i][1], result)
    39.                     res += result
    40.                 }
    41.             }
    42.             return res
    43.         }
    44.         // // 请用示例验证运行结果:
    45.         let arr = Array(20).fill(20).map(() => Math.ceil(Math.random() * 10))
    46.         add(arr).then(result => {
    47.             console.log(result) // 3
    48.             endTime = new Date().getTime()
    49.             console.log(endTime - starttime)
    50.         })