60. 排列序列

这道题虽然是困难的，但它本质上就是个找规律题，考察程序员基本功
看了一下别的题解，感觉写的都比我复杂，就不往上放了

代码：

class Solution {
    public String getPermutation(int n, int k) {
        int[] record = new int[n];
        k=k-1;
        Arrays.fill(record, 1);
        String result = "";
        int length = record.length;
        while (n > 0) {
            int jieCeng = getJieCeng(n - 1);
            int i = k / jieCeng, f = -1, j = 0;
            for (; j < length; j++) {
                if (record[j] == 1) f++;
                if (f == i) break;
            }
            record[j] = 0;
            result += j+1;
            n--;
            k %= jieCeng;
        }
        return result;

    }

    public int getJieCeng(int n) {
        int result = 1;
        for (int i = 1; i <= n; i++) {
            result *= i;
        }
        return result;
    }
}