LeetCode | 17. Letter Combinations of a Phone Number
2017-04-17 15:05
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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.
Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.
两种方法,一种是递归(3ms),另一种看的大神解答,用迭代(0ms)
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.
两种方法,一种是递归(3ms),另一种看的大神解答,用迭代(0ms)
//递归 class Solution { public: vector<char> tmp; vector<string> res; vector<string> Hash; void dfs(string digits,int index,int len)//处理第index位 { if(index == len) { string t = ""; for(int i=0;i<tmp.size();i++) { t += tmp[i]; } res.push_back(t); //tmp.erase(tmp.end()-1); return; } for(int i=0;i<Hash[digits[index]-'0'].length();i++) { tmp.push_back(Hash[digits[index]-'0'][i]); dfs(digits,index+1,len); tmp.erase(tmp.end()-1);//删除最后一个元素 } } vector<string> letterCombinations(string digits) { int len = digits.length(); if(len == 0) { return res; } Hash.push_back(""); Hash.push_back(""); Hash.push_back("abc"); Hash.push_back("def"); Hash.push_back("ghi"); Hash.push_back("jkl"); Hash.push_back("mno"); Hash.push_back("pqrs"); Hash.push_back("tuv"); Hash.push_back("wxyz"); dfs(digits,0,len); return res; } };
//迭代 class Solution { public: vector<string> letterCombinations(string digits) { vector<string> res; string charmap[10] = {"0", "1", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"}; if(digits.size() == 0) { return res; } res.push_back(""); for (int i = 0; i < digits.size(); i++) { vector<string> tmp; string chars = charmap[digits[i] - '0']; for (int c = 0; c < chars.size();c++) for (int j = 0; j < res.size();j++) tmp.push_back(res[j]+chars[c]); res = tmp; } return res; } };
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