17. Letter Combinations of a Phone Number (backtracking)
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"].
/**
* Return an array of size *returnSize.
* Note: The returned array must be malloced, assume caller calls free().
*/
char* digit2Letter(char digit){
switch(digit){
case '':
return "abc";
case '':
return "def";
case '':
return "ghi";
case '':
return "jkl";
case '':
return "mno";
case '':
return "pqrs";
case '':
return "tuv";
case '':
return "wxyz";
default:
return "";
}
} char** letterCombinations(char* digits, int* returnSize) {
char** returnArray = NULL;
if(*digits == '\0') return returnArray; char* returnElem = malloc(sizeof(char)*sizeof(strlen(digits)));
returnArray = malloc(sizeof(char*)*);
backTracking(digits, returnArray, returnSize, returnElem, ); return returnArray;
} void backTracking(char* digits, char** returnArray, int* returnSize, char* returnElem, int pElem){
if(*digits == '\0'){
(*returnSize)++;
char* elem = malloc(sizeof(char)*pElem);
memcpy(elem, returnElem, sizeof(char)*pElem);
elem[pElem] = '\0';
printf("elem[0] = %d, elem[1] = %d\n",elem[],elem[]);
returnArray[*returnSize-] = elem;
return;
} char* str = digit2Letter(*digits);
int len = strlen(str);
for(int i = ; i < len; i++){
returnElem[pElem] = str[i]; backTracking(digits+, returnArray, returnSize, returnElem, pElem+ );
}
}
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