?

你有一套活字字模?tiles，其中每個字模上都刻有一個字母?tiles[i]。返回你可以印出的非空字母序列的數目。示例 1：輸入："AAB" 輸出：8 解釋：可能的序列為 "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA"。 示例 2：輸入："AAABBC" 輸出：188提示：1 <= tiles.length <= 7 tiles 由大寫英文字母組成

?

public class Solution {public int NumTilePossibilities(string tiles){var set = new HashSet<string>();var list = tiles.ToList();// brute force all lengths// length options: 1, 2, 3, 4, 5, 6, 7for (int i = 1; i <= tiles.Length; i++){NumTilePossibilitiesHelper(new StringBuilder(), set, list, i);}return set.Count;}private static void NumTilePossibilitiesHelper(StringBuilder sequence, HashSet<string> set, List<char> tiles, int length){// base case if (sequence.Length == length){set.Add(sequence.ToString());return;}// please consider the next char for all possible charsint backtrackingLength = sequence.Length;for (int i = 0; i < tiles.Count; i++){var current = tiles[i];sequence.Append(current);// remove current char from the listtiles.RemoveAt(i);NumTilePossibilitiesHelper(sequence, set, tiles, length);// insert current char to the list// List.Insert()tiles.Insert(i, current);// StringBuilder.Remove(start, length)sequence.Remove(backtrackingLength, sequence.Length - backtrackingLength);}} }

?

總結

以上是生活随笔為你收集整理的c# leetcode1079. 活字印刷(回溯算法)的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。