题目:
题解:
class Solution {public String getPermutation(int n, int k) {int[] factorial = new int[n];factorial[0] = 1;for (int i = 1; i < n; ++i) {factorial[i] = factorial[i - 1] * i;}--k;StringBuffer ans = new StringBuffer();int[] valid = new int[n + 1];Arrays.fill(valid, 1);for (int i = 1; i <= n; ++i) {int order = k / factorial[n - i] + 1;for (int j = 1; j <= n; ++j) {order -= valid[j];if (order == 0) {ans.append(j);valid[j] = 0;break;}}k %= factorial[n - i];}return ans.toString();}
}