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The set
[1,2,3,…,n]
contains a total of n! unique permutations.
By listing and labeling all of the permutations in order,
We get the following sequence (ie, for n = 3):
We get the following sequence (ie, for n = 3):
"123"
"132"
"213"
"231"
"312"
"321"
Given n and k, return the kth permutation sequence.
Note: Given n will be between 1 and 9 inclusive.
» Solve this problem- 小小感叹一下,最近老是犯困,刷题太慢,智商又捉急,那群一周刷完leetcode的娃们佩服毅力,总是刷一会儿玩儿一会儿,真想踹自己。
嗯好吧,第一个按照之前permutation的思路,老解法递归去做,时间超了,显然就不行了。和之前permutation不同的是,它不需要把所有的permutation都输出,所以只需要找到这个东东排序的规律就好啦。所以直接loop搞起。
后一种做法,数学找规律,就是按照k和n来计算每一位是哪个数字,思路不难,就是中间细节处理麻烦。比如第一个数字是 k/(n-1)!, 然后再同样去考虑后面n-1个数。
后一种做法,数学找规律,就是按照k和n来计算每一位是哪个数字,思路不难,就是中间细节处理麻烦。比如第一个数字是 k/(n-1)!, 然后再同样去考虑后面n-1个数。
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