找出0-400亿中所有1的个数，求大神支招！！！
试了for循环 内存直接爆掉
14 回复
调试了一会发现这是一道数学题啊。
'use strict';
module.exports = main();
function counts(min, max) {
return new Promise(resolve => {
let result = 0;
for (let i = min; i < max; i++) {
result += count(i);
}
resolve(result);
});
}
function count(num) {
const len0 = (num + '').length;
const len1 = (num + '').replace(/1/g, '').length;
return len0 - len1;
}
async function main() {
const start = 1;
const end = 400000000;
const step = 20000;
async function reduce(sum, next) {
let num = next;
next = next + step;
if (next > end) return sum + await counts(num, end + 1);
return await reduce(sum + await counts(num, next), next);
}
const time = Date.now();
const result = await reduce(0, start);
console.log(`(${start}, ${end}), step=${step}，耗时：${(Date.now() - time) / 1000}，结果：${result}`);
}
这是数学问题了啊。。。
function main(max) {
let maxSp = max.toString().split('');
let maxSpFirst = maxSp[0];
let maxSpCalacuLen = Math.max(0, maxSp.length - 1);
let maxSpCalacuLen_1 = Math.max(0, maxSpCalacuLen-1);
let maxCountOnes = maxSpFirst * Math.pow(10, maxSpCalacuLen_1) * maxSpCalacuLen + Math.pow(10, maxSpCalacuLen);
console.log(`${maxSp},${maxSpFirst},${maxSpCalacuLen},${maxSpCalacuLen_1}:`,maxCountOnes);
}
