Leetcode 1079. Movable type printing

Leetcode 1079. Movable type printing

topic

你有一套活字字模 tiles，其中每个字模上都刻有一个字母 tiles[i]。返回你可以印出的非空字母序列的数目。

注意：本题中，每个活字字模只能使用一次。

Example 1:

输入："AAB"
输出：8
解释：可能的序列为 "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA"。

Example 2:

输入："AAABBC"
输出：188

Ideas

• Since the size of tiles is very small, you can consider using recursion to solve the problem
• First write a recursive processing subset problem-only consider the increase of one character at a time, use find to remove duplication
• After getting the subset, use full permutation, and use map to remove duplicates. Finally, -1 is to remove the empty set

Code

class Solution {
public:
    void dfs(vector<string>& res, string& tiles, string temp, int start) {
        if (find(res.begin(), res.end(), temp) == res.end()) {
            res.push_back(temp);
        }

        if (start >= tiles.size()) return;

        for (int i = start;i < tiles.size();++i) {
            dfs(res, tiles, temp + tiles[i], i + 1);
        }
    }

    int numTilePossibilities(string tiles) {
        vector<string> res;
        string temp;
        dfs(res, tiles, temp, 0);
        map<string, bool> mp;

        for (auto& s:res) {
            sort(s.begin(), s.end());

            do {
                if (mp[s] == false) {
                    mp[s] = true;
                }
            } while (next_permutation(s.begin(), s.end()));
        }

        return mp.size() - 1;
    }
};