In this post, we are going to solve the Letter Combinations of a Phone Number Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.
Problem
Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order.
A mapping of digits to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.
Example 1:
Input: digits = "23" Output: ["ad","ae","af","bd","be","bf","cd","ce","cf"]
Example 2:
Input: digits = "" Output: []
Example 3:
Input: digits = "2" Output: ["a","b","c"]
Constraints:
0 <= digits.length <= 4digits[i]is a digit in the range['2', '9']
Now, let’s see the leetcode solution of Letter Combinations of a Phone Number Leetcode Solution.
Letter Combinations of a Phone Number Leetcode Solution in Python
class Solution(object):
def letterCombinations(self, digits):
"""
:type digits: str
:rtype: List[str]
"""
dic = { "2": "abc", "3": "def", "4":"ghi", "5":"jkl", "6":"mno", "7":"pqrs", "8":"tuv", "9":"wxyz"}
res=[]
if len(digits) ==0:
return res
self.dfs(digits, 0, dic, '', res)
return res
def dfs(self, nums, index, dic, path, res):
if index >=len(nums):
res.append(path)
return
string1 =dic[nums[index]]
for i in string1:
self.dfs(nums, index+1, dic, path + i, res)Letter Combinations of a Phone Number Leetcode Solution in CPP
class Solution {
public:
vector<string> ans;
string keyPad[10] = {"", "", "abc", "def", "ghi", "jkl", "mno", "qprs", "tuv", "wxyz"};
void backtrack(int index, string& path, const string& digits) {
if (index == digits.size()) {
ans.push_back(path);
return;
}
for (char c : keyPad[digits[index] - '0']) {
path[index] = c;
backtrack(index + 1, path, digits);
}
}
vector<string> letterCombinations(const string& digits) {
if (digits.empty()) return ans;
string path = digits;
backtrack(0, path, digits);
return ans;
}
};Letter Combinations of a Phone Number Leetcode Solution in Java
class Solution {
String[] keyMapping = {"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
public void comboRecursive(String digits, String asf, List<String> ans){
if(digits.length()==0){
ans.add(asf);
return;
}
char firstDigit = digits.charAt(0);
String digitLeft = digits.substring(1);
String key = keyMapping[Integer.parseInt(""+firstDigit)];
for(char ch : key.toCharArray()){
comboRecursive(digitLeft,""+asf+ch,ans);
}
}
public List<String> letterCombinations(String digits) {
List<String> ans = new ArrayList<>();
if(digits.equals("")) return ans;
comboRecursive(digits,"",ans);
return ans;
}
}Note: This problem Letter Combinations of a Phone Number is generated by Leetcode but the solution is provided by Chase2learn This tutorial is only for Educational and Learning purposes.
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