leetcode Letter Combinations of a Phone Number

最新推荐文章于 2020-08-10 10:20:18 发布

原创最新推荐文章于 2020-08-10 10:20:18 发布 · 608 阅读

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本文介绍了一种算法，该算法接收一个数字字符串作为输入，并返回所有可能的字母组合，这些组合对应于电话按键上的字母。通过深度优先搜索实现，文章详细展示了如何创建数字到字母的映射，并递归地构建所有可能的组合。

Letter Combinations of a Phone NumberJan 27 '125504 / 16698

Given a digit string, return all possible letter combinations that the number could represent.

A mapping of digit to letters (just like on the telephone buttons) is given below.

Input:Digit string "23"
Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].

Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.

class Solution {

private:
    map<char, vector<char> > dict;
    vector<string> ret;

public:

    void createDict()
    {
        dict.clear();
        dict['2'].push_back('a');
        dict['2'].push_back('b');
        dict['2'].push_back('c');
        dict['3'].push_back('d');
        dict['3'].push_back('e');
        dict['3'].push_back('f');
        dict['4'].push_back('g');
        dict['4'].push_back('h');
        dict['4'].push_back('i');
        dict['5'].push_back('j');
        dict['5'].push_back('k');
        dict['5'].push_back('l');
        dict['6'].push_back('m');
        dict['6'].push_back('n');
        dict['6'].push_back('o');
        dict['7'].push_back('p');
        dict['7'].push_back('q');
        dict['7'].push_back('r');
        dict['7'].push_back('s');
        dict['8'].push_back('t');
        dict['8'].push_back('u');
        dict['8'].push_back('v');
        dict['9'].push_back('w');
        dict['9'].push_back('x');
        dict['9'].push_back('y');
        dict['9'].push_back('z');
    }

    void dfs(int depth, int maxdepth, string digits, string value)
    {
        if(depth == maxdepth)
        {
            ret.push_back(value);
        }
        for(int i=0; i<dict[digits[depth]].size(); i++)
        {
            dfs(depth+1, maxdepth, digits, value+dict[digits[depth]][i]);
        }
    }
    vector<string> letterCombinations(string digits) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
       createDict();
       ret.clear();
       string temp;
       dfs(0, digits.size(), digits, temp);
       return ret;
    }



};