In the Leetcode Letter Combinations of a Phone Number problem solution in C programming 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.
Leetcode Letter Combinations of a Phone Number problem solution in C programming
char** letterCombinations(char* digits, int* returnSize) {
char letterMatrix[10][5] = {" ", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
char letterLength[10] = {1, 1, 3, 3, 3, 3, 3, 4, 3, 4};
bool empty = true;
int count = 1;
int length = strlen(digits);
for (int i = 0; i < length; i++) {
int digit = digits[i] - '0';
if (letterLength[digit] > 0) {
empty = false;
count *= letterLength[digit];
}
}
if (empty) {
*returnSize = 0;
return NULL;
}
*returnSize = count;
char **result = calloc(count, sizeof(char *));
for (int i = 0; i < count; i++) {
*(result + i) = calloc(length + 1, sizeof(char));
}
int blockLeap = count;
int blockNum = 1;
for (int i = 0; i < length; i++) {
int currentDigit = digits[i] - '0';
int n = letterLength[currentDigit];
int letterLeap = blockLeap / n;
for (int j = 0; j < n; j++) {
for (int k = 0; k < blockNum; k++) {
for (int l = 0; l < letterLeap; l++) {
result[l + j * letterLeap + k * blockLeap][i] = letterMatrix[currentDigit][j];
}
}
}
blockLeap /= n;
blockNum *= n;
}
return result;
}Also read,
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