排列序列
07/06/2021
题目描述
给出集合 [1,2,3,...,n]，其所有元素共有 n! 种排列。
按大小顺序列出所有排列情况，并一一标记，当 n = 3 时, 所有排列如下：
"123"
"132"
"213"
"231"
"312"
"321"
给定 n 和 k，返回第 k 个排列。
示例 1：
输入：n = 3, k = 3
输出："213"
示例 2：
输入：n = 4, k = 9
输出："2314"
示例 3：
输入：n = 3, k = 1
输出："123"
提示：
- 1 <= n <= 9
- 1 <= k <= n!
本人题解
/**
* @param {number} n
* @param {number} k
* @return {string}
*/
var getPermutation = function(n, k) {
let arr = [1,2,3,4,5,6,7,8,9],
m1 = 1, m2 = m1*2, m3 = m2*3, m4 = m3*4,
m5 = m4*5, m6 = m5*6, m7 = m6*7, m8 = m7*8,
m9 = m8*9, mMap = [m1, m2, m3, m4, m5, m6, m7, m8, m9];
let result = '';
while (n > 0) {
if(n == 1) {
result = result + arr[n-1]
n--
} else {
let index = Math.floor((k-1)/mMap[n-2]);
let num = arr.splice(index, 1);
result = result + num[0]
k = ((k-1) % mMap[n-2]) + 1
n--;
}
}
return result;
};第二次 2025-3-14
var getPermutation = function(n, k) {
const nums = [1,2,3,4,5,6,7,8,9]
const sort1 = 1, sort2 = sort1 * 2, sort3 = sort2 * 3, sort4 = sort3 * 4, sort5 = sort4 * 5, sort6 = sort5 * 6, sort7 = sort6 * 7, sort8 = sort7 * 8, sort9 = sort8 * 9;
const sortMap = {
1: sort1,
2: sort2,
3: sort3,
4: sort4,
5: sort5,
6: sort6,
7: sort7,
8: sort8,
9: sort9,
}
let result = ""
while (n > 1) {
let index = Math.ceil(k / (sortMap[n - 1]))
k = k % (sortMap[n - 1])
if (index === 0) {
index = n
}
result += nums[index - 1]
nums.splice(index - 1, 1)
n--
}
result += nums[0]
return result;
};
## 分析
忘了。以后再补