[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 · 623 阅读

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本文介绍了一种基于递归深度优先搜索的算法，用于根据输入的数字字符串生成所有可能的字母组合。数字到字母的映射遵循标准的电话键盘布局。

class Solution {
private:
    map<char, vector<char> > dict;

public:
    vector<string> letterCombinations(string digits) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function

         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');
         
         vector<string> res;

         dfs(digits, 0, "", res);
         
         return res;
    }
    
    void dfs(string& dig, int idx, string cur, vector<string>& res)
    {
        if (idx == dig.size())
        {
            res.push_back(cur);
            return;
        }
            
        for (int i = 0; i < dict[dig[idx]].size(); ++i)
        {
            dfs(dig, idx + 1, cur + dict[dig[idx]][i], res);
        }
    }
};