LeetCode--letter-combinations-of-a-phone-number

最新推荐文章于 2020-04-23 22:58:57 发布

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本文介绍了一种基于电话按键映射实现数字字符串转换为所有可能的字母组合的方法。使用深度优先搜索法进行递归回溯，实现了数字到字母的有效转换。

题目描述

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.

分析：深度优先搜索法，递归回溯

class Solution {
    string dic[10]={"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
    string d="";
    vector<string> z;
public:
    vector<string> letterCombinations(string digits) {
        dfs(digits,0);
        return z;
    }
    void dfs(string digits,int idex)
    {
        if(idex==digits.length()) z.push_back(d);
        else
        {
            int i,t=digits[idex]-'0';
            string str=dic[t];
            for(i=0;i<str.length();i++)
            {
                string str1=d;
                d+=str[i];
                dfs(digits,idex+1);  //深度优先搜索
                d=str1;  //回溯
            }
        }
    }
};