This program implements T9 dictionary

t9_dictionary.c

#define MAX_NUMBER_LENGTH 3 
const char hashTable[10][4] = {"", "",
                          "abc", "def",
                          "ghi", "jkl",
                          "mno", "pqrs",
                          "tuv", "wxyx"};


void  printWords(int number[], int curr_digit, char output[]){

   int i;
   if(curr_digit == MAX_NUMBER_LENGTH){
         printf("%s\n", output);
         return ;
   }

   for(i=0; i<strlen(hashTable[curr_digit]); i++){
       output[curr_digit] = hashTable[(number[curr_digit])][i];
       printWords(number, curr_digit+1, output);
       if(number[curr_digit] == 0 || number[curr_digit] == 1)
           return;
   }
}
void T9_dictionary(int number[], int n){
        char result[n +1] ;
        result[n] ='\0';
        printWords(number, 0, result);
} 

/* Driver program to execute above code */
int main(void)
{
    int number[] = {2, 3, 4};
    int n = sizeof(number)/sizeof(number[0]);
    T9_dictionary(number,n)
    return 0;
}