17. Letter Combinations of a Phone Number

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最新推荐文章于 2024-01-18 13:57:19 发布

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分类专栏： Leetcode

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本文介绍了一个经典的编程问题——电话号码的字母组合。给定一个数字字符串，返回所有可能的字母组合，这些组合由电话键盘上的数字映射而来。通过递归算法解决该问题，并提供了一段C++代码实现。

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题目：

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"].

枚举递归

class Solution {
public:
    map<int,string> m={{2,"abc"},{3,"def"},{4,"ghi"},{5,"jkl"},{6,"mno"},{7,"pqrs"},{8,"tuv"},{9,"wxyz"}};
    vector<string> letterCombinations(string digits) {
         vector<string> res;
        string temp;
        if(digits.empty())          
            return res;    
        solve(digits,0,res,temp);
        return res;
    }
    
    void solve(string digits,int index,vector<string> &res,string temp){
        if(index==digits.size())
            res.push_back(temp);
        int i=digits[index]-'0';
        for(int j=0;j<m[i].size();j++){
            solve(digits,index+1,res,temp+m[i][j]);
        }
    }
};