Letter Combinations of a Phone Number
发布时间：2020-12-13 20:05:00 所属栏目：PHP教程 来源：网络整理
导读：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]. N
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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: 用dfs解决 class Solution {
public:
vector<string> letterCombinations(string digits) {
vector<string>ans;
dfs(digits,"",ans);
return ans;
}
void dfs(string digits,int start,string s,vector<string>&ans){
if(start == digits.size()){
if(s != "")
ans.push_back(s); return;
}
int cnt = digits[start]-'2';
for(int i = 0; i < 4; i++)
if(letter[cnt][i] != '!')
dfs(digits,start+1,s+letter[cnt][i],ans);
}
char letter[8][4] = {
{'a','b','c','!'},{'d','e','f',{'g','h','i',{'j','k','l',{'m','n','o',{'p','q','r','s'},{'t','u','v',{'w','x','y','z'}
};
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