Leetcode 60 Permutation Sequence

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):

1. "123"
2. "132"
3. "213"
4. "231"
5. "312"
6. "321"

Given n and k, return the kth permutation sequence.

Note: Given n will be between 1 and 9 inclusive.

输出长度为n的数字串字典序的第K个串。

每一位定下来以后，后面共有(n-1)!个排列，运用这个特点反复减k，让k去逼近1。

代码语言：javascript复制

class Solution {
public:
    string getPermutation(int n, int k) {
        int mp[10];
        mp[0]=mp[1]=1;
        vector<int> v(1,1);
        for(int i=2;i<10;i  )
        {
            mp[i]=mp[i-1]*i;
            v.push_back(i);
        }
        string result;
        while(n--)
        {
            vector<int>::iterator it=v.begin();
            while(k>mp[n])
            {
                k-=mp[n];
                it  ;
            }
            result =('0' *it);
            v.erase(it);
        }
        return result;
    }
};

permutation return sequence set unique

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