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.
A easy problem. Do DFS to construct the results.
C++ Code:
/* * func: letter_combinations_helper * goal: DFS search function to construct results * @param digits: remaining digits string * @param output: current output string * @param result: result set * return: no return value needed */ void letter_combinations_helper(string digits, string output, vector<string> &result,){ if(digits.size() == 0){ //No more digits reading need result.emplace_back(output); return; } switch(digits[0]){ case '2': letter_combinations(digits.substr(1), result, output + 'a'); letter_combinations(digits.substr(1), result, output + 'b'); letter_combinations(digits.substr(1), result, output + 'c'); break; case '3': letter_combinations(digits.substr(1), result, output + 'd'); letter_combinations(digits.substr(1), result, output + 'e'); letter_combinations(digits.substr(1), result, output + 'f'); break; case '4': letter_combinations(digits.substr(1), result, output + 'g'); letter_combinations(digits.substr(1), result, output + 'h'); letter_combinations(digits.substr(1), result, output + 'i'); break; case '5': letter_combinations(digits.substr(1), result, output + 'j'); letter_combinations(digits.substr(1), result, output + 'k'); letter_combinations(digits.substr(1), result, output + 'l'); break; case '6': letter_combinations(digits.substr(1), result, output + 'm'); letter_combinations(digits.substr(1), result, output + 'n'); letter_combinations(digits.substr(1), result, output + 'o'); break; case '7': letter_combinations(digits.substr(1), result, output + 'p'); letter_combinations(digits.substr(1), result, output + 'q'); letter_combinations(digits.substr(1), result, output + 'r'); letter_combinations(digits.substr(1), result, output + 's'); break; case '8': letter_combinations(digits.substr(1), result, output + 't'); letter_combinations(digits.substr(1), result, output + 'u'); letter_combinations(digits.substr(1), result, output + 'v'); break; case '9': letter_combinations(digits.substr(1), result, output + 'w'); letter_combinations(digits.substr(1), result, output + 'x'); letter_combinations(digits.substr(1), result, output + 'y'); letter_combinations(digits.substr(1), result, output + 'z'); break; default: letter_combinations(digits.substr(1), result, output); break; } } /* * func: letter_combinations_helper * goal: to find all possible combinations based on input digits * @param digits: input digits string * return: vector containing all possible combinations */ vector<string> letter_combinations(string digits) { vector<string> result; letter_combinations_helper(digits, "", result,); return result; }
Python Code:
# func: to find all possible combinations based on input digits # @param digits: input digits string # @return: all possible combinations def letter_combinations(digits): num_dict = {'2': 'abc', '3': 'def', '4': 'ghi', '5': 'jkl', '6': 'mno', '7': 'pqrs', '8': 'tuv', '9': 'wxyz'} result = [''] for digit in digits: if digit in '23456789': result = [x + letter for x in result for letter in num_dict[digit]] return result
No comments:
Post a Comment