#17 Letter Combinations of a Phone Number
题目链接:https://leetcode.com/problems/letter-combinations-of-a-phone-number/
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:
Although the above answer is in lexicographical order, your answer could be in any order you want.
/** * Return an array of size *returnSize. * Note: The returned array must be malloced, assume caller calls free(). */ void SubCombination(char* digits, char map[][5], char* output, char** ret, int* returnSize, int k) { //k表示递归到当前字母的下标 int i = 0; if(digits[k] == '\0') { //基准情况;递归到字符串结束处。将当前输 output[k] = '\0'; if(k) strcpy(ret[(*returnSize)++], output); //复制字符串到输出数组 return; } while(map[digits[k] - '0'][i]) { //当前数字相应的每个字母进行递归 output[k] = map[digits[k] - '0'][i]; SubCombination(digits, map, output, ret, returnSize, k + 1); ++i; } } char** letterCombinations(char* digits, int* returnSize) { *returnSize = 0; char map[10][5] = {"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"}; char output[20] = {}; //输出字符串 char **ret = (char **)malloc(sizeof(char *) * 1000); for(int i = 0; i < 1000; ++i) ret[i] = (char *)malloc(sizeof(char) * 20); SubCombination(digits, map, output, ret, returnSize, 0); //从第一个字母開始递归保存每个数字相应字母,到结尾处保存相应字符串 return ret; }