**LeetCode 60. Permutation Sequence

https://leetcode.com/problems/permutation-sequence/

康拓展开和逆康拓展开

自己推一推  参考http://www.cnblogs.com/hxsyl/archive/2012/04/11/2443009.html

class Solution {public:    string getPermutation(int n, int k) {        k--;        for(int i=0;i<=n;i++){            vis[i]=0;            if(i == 0)jie[i]=1;            else jie[i] = (i)*jie[i-1];        }        string ret;        for(int i=n-1;i>0;i--) {            int div = k/jie[i];            int mod = k%jie[i];            ret = ret + getDiv(div+1,n);            //cout << "div=" << div << "  " << "  mod=" << mod << endl;            k = mod;        }        for(int i=1;i<=n;i++)            if(!vis[i])                ret = ret + (char)(i+'0');        return ret;    }    char getDiv(int d, int n) {        int cnt=0;        for(int i=1;i<=n;i++) {            if(!vis[i]) {                cnt++;                if( cnt == d ) {                    vis[i] = 1;                    return (char)(i+'0');                }            }        }        return '0';    }private:    int vis[10], jie[10];};