#include <iostream>
using namespace std; 

/********************
 *
 *  C-style strings
 *
 ********************/

// In C strings are char arrays 
// note that the size of the array is 6 but the number of characters appears to be 5
// that is because the last character is a Null character '\0' when you assign values in ""
// to print strings in C, include stdio.h

#include <cstdio>               // for printf(). Also <cstdio> would do

/*
int main() {
  char str[6] = "ABCDE"; 
  printf("str = %s \n", str);    // printf() is cout of C. %s is a placeholder for a string

  char str2[200];
  scanf("%s", str2); //scanf() is cin of C
  printf("You entered: %s \n", str2);

  int i = 67; 
  printf("i = %i \n", i ); 
  printf("i = %d \n", i ); 
  printf("i = %c \n", i ); 
}
*/

// other placeholders for printf: %c for char, %i and %d for int, %f for float and double...

// string library 

#include <string.h>      // Also <cstring>

// strlen( str ) - returns the number of characters without NULL character
// strcmp( str1, str2 ) - returns the difference between 2 strings. 0 if they are same
// strcpy( dest, src ) - copies src into dest 
// strncpy( dest, src, n ) - copies first n chars from src into dest

// search functions
// strchr ( str, char ) - returns a pointer to the first occurance of char in str
// strstr ( str, searchstr ) - returns a pointer to the first occurance of searchstr in str

// ex: 

/*
int main() {
  char s1[6] = "ABCDE"; 
  char s2[6] = "gf"; 
  
  int len = strlen(s1); 
  printf("length of s1: %i \n", len ); 
  printf("length of s1: %d \n", strlen(s1)); 
  printf("length of %s is %d \n", s1, strlen(s1)); 

  // s1 = s2;      // ILLEGAL
  // s1 = "fgsdf"; // ILLEGAL
  strncpy( s1, s2, strlen(s2) );
  printf("s1: %s \n", s1 ); 

  strcpy( s2, s1 ) ; 
  printf("s2: %s \n", s1 ); 
  
  char s3[6] = "gfCDF"; 
  printf("comparing s2 and s3: %d \n", strcmp(s2,s3)); 
 
  return 0;
} 
*/


/***************
 *
 *  File I/O 
 *
 ***************/

// related data
// sequential access - imagine a cursor sits at a position in the file. last position - eof

/* 3 steps involved: 
    1) open file ( reading || writing )
    2) read from || write to the file
    3) close file 
*/


// include header <fstream> - contains ifstream (input file) and ofstream (output file) classes 

#include <fstream> 

// reading example 
/*
int main(){
  ifstream inFile; 
  inFile.open("myfile.dat", ios::in);  // ios::in is the mode to open the file. in is for reading
  
  // ifstream inFile("myfile.dat", ios::in); 

  // check if the file opened properly
  if ( !inFile ) {
    cout << "Error opening file!" << endl ;
    return 1;
  }

  // read first 2 numbers
  int x, y; 
  inFile >> x; 
  inFile >> y;       // OR inFile >> x >> y; 

  // read the rest 
  while( !inFile.eof() ) {
    inFile >> x ; 
    cout << "x = " << x << endl ;
  }

  inFile.close();

  return 0;
}
*/

// writing example
/*
int main(){
  ofstream outFile; 
  outFile.open("../outfile.dat", ios::out);  // out - open the file writing, app - to append

  // check if the file opened properly
  if ( !outFile ) {
    cout << "Error opening file!" << endl ;
    return 1;
  }

  int x = 3; 
  outFile << "Hello, world! \n"; 
  outFile << "x = " << x << endl ;       

  outFile.close();

  return 0;
}
*/

/***********************************
 *
 *  Character handling  w/ ctype.h 
 *
 ***********************************/

// character handling library of C 

#include <ctype.h>

// some useful functions:
// isdigit(char) - returns true if char is 0..9
// isalpha(char) - returns true if char is A..Z or a..z
// isalnum(char) - returns true if char is a digit or alphabet
// islower(char) - returns true if a..z
// isupper(char) - returns true if A..Z

// How do these functions work? -> ASCII table 
// 0 - 9  in ASCII 48 - 57 
// A - Z  in ASCII 65 - 90 
// a - z  in ASCII 97 - 122 
 
// OR If you want to check the ASCII value of a character: 
/*
int main(){
  char c = 'a'; 
  int ascii_val = c; 
  cout << "ascii value of '" << c << "' is = " << ascii_val << endl; 
}
*/

// ex1: write a program that counts the number of upper case, lower case and numeric characters
// in a user provided string

#include <cctype>
#include <cstdio>
#include <cstring> 
/*
int main() {
  
  // read input from user
  printf("Enter a string: ");
  char str[100]; 
  scanf("%s", str);

  // count #digits, #upper, #lower

  int d = 0, u = 0, l =0; 
  for( int i=0; i < strlen(str); i++ ){
    if ( isdigit(str[i]) )
      d++; 
    if ( isupper(str[i]) )
      u++;
    if ( islower(str[i]) )
      l++;
  }


  // display results 
  printf("#digits = %i, #upper case letters = %i, #lower case letters = %i \n",d,u,l);
  return 0;
}
*/
// ex2: modify the above program to write upper case letters in a file called "upper.dat"
//     and lower case letters in a file called "lower.dat"


#include <cctype> 
#include <fstream> 
#include <cstring>
#include <cstdio>

int main() {
  
  printf("Enter string: "); 
  char str[100];
  scanf("%s", str); 

  ofstream outUpper, outLower; 
  outUpper.open("upper.dat", ios::out); 
  outLower.open("lower.dat", ios::out); 

  for(int i=0; i< strlen(str); i++){
    if ( isupper(str[i]) ){
      outUpper << str[i] ; 
    }
    if ( islower(str[i]) ){
      outLower << str[i] ;
    }
  }

  outUpper.close(); 
  outLower.close();
  
  return 0;
}