2020.3.8 Vivo笔试
第一次发帖，紧张
使用语言JavaScript
1、相当于计算数列 1，2，2，3，3，3，4，4，4，4，5……前n项的和
function solution(n) {
const x = Math.floor(Math.sqrt(1 + 8 * n) / 2 - 0.5);
const remain = n - ((1 + x) * x) / 2;
let result = 0;
for (let i = 1; i <= x; i++) {
result += i ** 2;
}
result += remain * (x + 1);
return result;
} 2、找出每位乘积为n的最小数，如36=>49(4*9=36)，2=>12(1*2=2) function solution(n) {
let result = '';
let tmp = n;
for (let i = 9; i > 1; i--) {
while (!(tmp % i)) {
tmp /= i;
result = i + result;
}
}
while (tmp === 1 && result.length < 2) {
result = 1 + result;
}
if (tmp !== 1) {
return -1;
} else {
return parseInt(result);
}
} 3、给定最大长度n和最小长度m，求锁屏图案密码的总数。其实就是找有多少个长度在m到n之间的符合规则的点序列。 /* 1 2 3
4 5 6
7 8 9
*/
function isCorrect(path, point) {
const lines = [
[1, 2, 3],
[4, 5, 6],
[7, 8, 9],
[1, 4, 7],
[2, 5, 8],
[3, 6, 9],
[1, 5, 9],
[3, 5, 7]
];
if (path.length === 0) {
return true;
}
if (path.indexOf(point) !== -1) {
return false;
}
let point1 = path[path.length - 1];
let point2 = point;
if (point2 < point1) {
[point1, point2] = [point2, point1];
}
for (let line of lines) {
if (
point1 === line[0] &&
point2 === line[2] &&
path.indexOf(line[1]) === -1
) {
return false;
}
}
return true;
}
function solution(m, n) {
let count = 0;
function solve(path, remain) {
if (remain <= max - min) {
count++;
}
if (remain === 0) {
return;
}
for (let i = 1; i <= 9; i++) {
if (isCorrect(path, i)) {
path.push(i);
solve(path, remain - 1);
path.pop();
}
}
}
const min = Math.max(1, m);
const max = Math.min(9, n);
let path = [];
solve(path, max);
return count;
} 不过上面能过的话下面的解也能过（而且肯定快，不过你要把每一项先算出来emmm）
function solution(m, n) {
const result = [9, 56, 320, 1624, 7152, 26016, 72912, 140704, 140704];
const min = Math.max(1, m);
const max = Math.min(9, n);
return result.slice(min - 1, max).reduce((pre, cur) => pre + cur, 0);
} 
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