// SMS Problem (Multiple Key Press) - #-Break, 1 - NULL, 2 - ABC2, ...etc 
//

//#define DEBUG_PRINT

#include <stdio.h>

char*  MultiKeyStrokeParser(char *pKeys);
void PrintParsedText(char *pKeys);

int main(int argc, char *args[])
{
  printf("\n");

  PrintParsedText("22");        // B
  PrintParsedText("23");        // AD
  PrintParsedText("223");       // BD
  PrintParsedText("22#2");      // BA (# breaks the cycle)
  PrintParsedText("3#33");      // DE
  PrintParsedText("2222");      // 2
  PrintParsedText("2222#2");    // 2A
  PrintParsedText("22222");     // A (cycle must wrap around)
  PrintParsedText("222222");    // B
  PrintParsedText("#33#44#");   // EH
  PrintParsedText("#44#444");   // HI
  PrintParsedText("#4*222#");   // G C
  PrintParsedText("33*222*4");  // E C G
}

void PrintParsedText(char *pKeys)
{
#ifdef DEBUG_PRINT
  printf("\n");
#endif

  char *pText = MultiKeyStrokeParser(pKeys);
  printf("Input Keys = %s, Output Text = %s\n", pKeys, pText ? pText : "NULL");
  if (NULL != pText) { free(pText); pText = NULL; }
}

char*  MultiKeyStrokeParser(char *pKeys)
{
  static char *pMappings[] = {
    "1", "2ABC", "3DEF", "4GHI", "5JKL", 
    "6MNO", "7PQRS", "8TUV", "9WXYZ"
  };
  
  int errorCode;
  int i, nText, nCount, nCh, j;
  int fConvert;
  int nKeys = strlen(pKeys);
  char *pText = NULL;
  char *pMap;

#ifdef DEBUG_PRINT
  printf("DEBUG : Input Keys = %s, Length = %d\n", pKeys, nKeys);
#endif

  pText = (char *) malloc((nKeys + 1) * sizeof(char));
  if (NULL == pText)
  {
    printf("ERROR : Insufficient memory!");
    errorCode = -1;
    goto Exit;
  }

  nText = 0; fConvert = 0;

  for (i = 0, nCount = 0, j = 0; j < nKeys; )
  {
    // Make sure only numbers, break (#), and space (*) are pressed
    //
    if ((pKeys[j] < '0' || pKeys[j] > '9') && 
        (pKeys[j] != '#') && (pKeys[j] != '*') && (pKeys[j] != '\0'))
    {
      printf("ERROR : Invalid Input Character!\n");
      errorCode = -2;
      goto Exit;
    }

    if (pKeys[i] == '#')
    {
      i++;
      nCount = 0;
      fConvert = 0;
      j = i;
    }
    else if (pKeys[i] == '*')
    {
      i++;
      nCount = 0;
      fConvert = 0;
      j = i;
      pText[nText++] = ' ';
    }
    else if (pKeys[i] == pKeys[j])
    {
      nCount++; j++; fConvert = 0;
    }
    else
    {
      fConvert = 1;
    }

    if (j == nKeys) 
      fConvert = 1;

    if (fConvert)
    {
      nCh = (int) (pKeys[i] - '0');
     
      if (nCh < 0 || nCh > 9) break;

      pMap = pMappings[nCh-1];

#ifdef DEBUG_PRINT
    printf("DEBUG : Char = '%c' / %d, Count = %d, Map = %s \n", pKeys[i], nCh, nCount, pMap);
#endif
      pText[nText++] = pMap[nCount % strlen(pMap)];
 
      i += nCount;
      j = i;
      fConvert = 0;
      nCount = 0;
    }
  }

  pText[nText++] = '\0'; // NULL Terminate
  errorCode = 0;

Exit:

  if (errorCode < 0)
  {
    free(pText);
    pText = NULL;
  }

  return pText;
}

Input Keys = 22, Output Text = B
Input Keys = 23, Output Text = AD
Input Keys = 223, Output Text = BD
Input Keys = 22#2, Output Text = BA
Input Keys = 3#33, Output Text = DE
Input Keys = 2222, Output Text = 2
Input Keys = 2222#2, Output Text = 2A
Input Keys = 22222, Output Text = A
Input Keys = 222222, Output Text = B
Input Keys = #33#44#, Output Text = EH
Input Keys = #44#444, Output Text = HI
Input Keys = #4*222#, Output Text = G C
Input Keys = 33*222*4, Output Text = E C G