[LeetCode]Letter Combinations of a Phone Number

原创于 2015-05-28 11:31:55 发布 · 495 阅读

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本文介绍了一种使用深度优先搜索算法来解决电话号码对应的字母组合问题的方法。通过递归调用，实现了所有可能的字母组合输出。

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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.

[LeetCode Source]

思路：深度优先搜索

class Solution {
public:
    vector<string> letterCombinations(string digits) {
        vector<string> ret;
        vector<string> Num = {"abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
        string temp;
        if(digits.size()==0)
            return ret;
        Dfs(digits,ret,Num,temp,0);
        return ret;
    }
    void Dfs(string digits,vector<string> &ret,vector<string>Num,string temp,int index){
        if(index==digits.size()){
            ret.push_back(temp);
            return;
        }
        int digit = digits[index]-'2';
        for(int i=0;i<Num[digit].size();++i ){
            temp.push_back(Num[digit][i]);
            Dfs(digits,ret,Num,temp,index+1);
            temp.pop_back();
        }
    }
};