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Permutation Sequence

2024-08-04 18:45:38   218人阅读

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.

 

参考：http://www.cnblogs.com/tenosdoit/p/3721918.html

 

C++实现代码：

#include<iostream>#include<string>#include<vector>using namespace std;class Solution {public:    string getPermutation(int n, int k) {        if(n==0)            return "";        int total=factorial(n);        string str=string("123456789").substr(0,n);        string ret(n,‘ ‘);        int i;        for(i=0;i<n;i++)        {            int index;            total=total/(n-i);            index=(k-1)/total;            ret[i]=str[index];            str.erase(index,1);            k=k-index*total;        }        return ret;    }    int factorial(int n)    {        if(n==0)            return 0;        int i;        int sum=1;        for(i=1;i<=n;i++)           sum*=i;        return sum;    }};int main(){    Solution s;    cout<<s.getPermutation(3,5)<<endl;}

 

Permutation Sequence


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