Permutation Sequence

最新推荐文章于 2024-08-15 00:02:14 发布

最新推荐文章于 2024-08-15 00:02:14 发布 · 62 阅读

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本文介绍了一种算法，用于找出数字集合 [1,2,3,...,n] 中第 k 个字典序排列。通过递减计数和列表移除的方法，实现了对 n 和 k 的输入返回对应的排列字符串。

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):

"123"
"132"
"213"
"231"
"312"
"321"

Given n and k, return the kth permutation sequence.

public class Solution {
    public String getPermutation(int n, int k) {
    	int t = 1;;
    	List<Integer> list = new ArrayList<Integer>();
    	for (int i = 1; i <= n; i++) {
    		t *= i;
    		list.add(i);
    	}
    	k--;
    	StringBuilder sb = new StringBuilder();
    	for (int i = n; i >= 1; i--) {
    		t = t/i;
    		int index = k/t;
    		sb.append(list.get(index));
    		list.remove(index);
    		k = k % t;
    	}
    	return sb.toString();
    }
}