Context: I am making myself a password generator in c++, basically it uses rand to generate numbers, and these numbers correspond directly to ASCII characters.
So, generating the numbers is easy, but i need to convert this to their ASCII equivalents to actually make a usable password.
#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;
int main ()
{
//Initializing variables.
int type = 0;
int character = 0;
char print = character;
//Generator.
srand(time(NULL));
for (int i=0; i<10;i++)
{
type = rand()%(3-1+1)+1;//Determines: 1 = Uppercase, 2 = Lowercase, 3 = Number.
if (type == 1)//If Uppercase.
{
character = rand()%(90-65+1)+65;//Determines Uppercase character to be generated.
cout<<print<<endl;
}
if (type == 2)//If Lowercase.
{
character = rand()%(122-97+1)+97;//Determine Lowercase character to be generated.
cout<<print<<endl;
}
if (type == 3)//If Numerical.
{
character = rand()%(57-48+1)+48;//Determines Number to be generated.
cout<<print<<endl;
}
}
}
In the code i posted above, you can see i last tried blatantly telling the program that the variable "character" needs to be used as an actually character.
Ok so there seems to be a bit of confusion.
Rand generates a number say between 65 and 90. These numbers correspond to capital letters on the ASCII table. I want to print to the console the letter, not the generated number.
When you write this
char print = character;
you tell the compiler that you want it to initialize variable print to the current value of variable character (which happens to be zero at the time). If you want the current value to be set to a variable of different type, you need to do it after a reassignment of character:
character = rand()%(90-65+1)+65;//Determines Uppercase character to be generated.
print = (char)character;
cout<<print<<endl;
You do not have to do reassignment, though, because a cast directly before printing will be sufficient:
character = rand()%(90-65+1)+65;//Determines Uppercase character to be generated.
cout<<(char)character<<endl;
Note: although it is fine to use decimal values of ASCII characters, the code becomes easier to read if you use character constants instead:
character = rand()%('Z'-'A'+1)+'A';
may be try by replacing
cout<<print<<endl;
by
cout<<(char)character;
Then you will understand what you missed.
In addition to Jay Kumars answer this is I believe an implicit/explicit conversion
Here is an example I tested with my code, it functions to this end.
for (int i = 0; i < size; ++i) {
cout << (char)('0' + 17 + i) << "-->\t"; // implicit conversion
}
Related
I am creating a small game where the user will have hints(Characters of a string) to guess the word of a string. I have the code to see each individual character of the string, but is it possible that I can see those characters printed out randomly?
string str("TEST");
for (int i = 0; i < str.size(); i++){
cout <<" "<< str[i];
output:T E S T
desired sample output: E T S T
Use random_shuffle on the string:
random_shuffle(str.begin(), str.end());
Edits:
C++11 onwards use:
auto engine = std::default_random_engine{};
shuffle ( begin(str), end(str), engine );
Use the following code to generate the letters randomly.
const int stl = str.size();
int stl2 = stl;
while (stl2 >= 0)
{
int r = rand() % stl;
if (str[r] != '0')
{
cout<<" "<<str[r];
str[r] = '0';
stl2--;
}
}
This code basically generates the random number based on the size of the String and then prints the character placed at that particular position of the string.
To avoid the reprinting of already printed character, I have converted the character printed to "0", so next time same position number is generated, it will check if the character is "0" or not.
If you need to preserve the original string, then you may copy the string to another variable and use it in the code.
Note: It is assumed that string will contain only alphabetic characters and so to prevent repetition, "0" is used. If your string may contain numbers, you may use a different character for comparison purpose
This question already has answers here:
How to strip all non alphanumeric characters from a string in c++?
(12 answers)
Closed 6 years ago.
I'm trying to remove all non alphabet characters from an inputed string in c++ and don't know how to. I know it probably involves ascii numbers because that's what we're learning about. I can't figure out how to remove them. We only learned up to loops and haven't started arrays yet. Not sure what to do.
If the string is Hello 1234 World&*
It would print HelloWorld
If you use std::string and STL, you can:
string s("Hello 1234 World&*");
s.erase(remove_if(s.begin(), s.end(), [](char c) { return !isalpha(c); } ), s.end());
http://ideone.com/OIsJmb
Note: If you want to be able to handle strings holding text in just about any language except English, or where programs use a locale other than the default, you can use isalpha(std::locale).
PS: If you use a c-style string such as char *, you can convert it to std::string by its constructor, and convert back by its member function c_str().
If you're working with C-style strings (e.g. char* str = "foobar") then you can't "remove" characters from a string trivially (as a string is just a sequence of characters stored sequentially in memory - removing a character means copying bytes forward to fill the empty space used by the deleted character.
You'd have to allocate space for a new string and copy characters into it as-needed. The problem is, you have to allocate memory before you fill it, so you'd over-allocate memory unless you do an initial pass to get a count of the number of characters remaining in the string.
Like so:
void BlatentlyObviousHomeworkExercise() {
char* str = "someString";
size_t strLength = ... // how `strLength` is set depends on how `str` gets its value, if it's a literal then using the `sizeof` operator is fine, otherwise use `strlen` (assuming it's a null-terminated string).
size_t finalLength = 0;
for(size_t i = 0; i < strLength; i++ ) {
char c = str[i]; // get the ith element of the `str` array.
if( IsAlphabetical(c) ) finalLength++;
}
char* filteredString = new char[ finalLength + 1 ]; // note I use `new[]` instead of `malloc` as this is C++, not C. Use the right idioms :) The +1 is for the null-terminator.
size_t filteredStringI = 0;
for(size_t i = 0; i < strLength; i++ ) {
char c = str[i];
if( IsAlphabetical(c) ) filteredString[ filteredStringI++ ] = c;
}
filteredString[ filteredStringI ] = '\0'; // set the null terminator
}
bool IsAlphabet(char c) { // `IsAlphabet` rather than `IsNonAlphabet` to avoid negatives in function names/behaviors for simplicity
return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
}
I do not want to spoil the solution so I will not type out the code, only describe the solution. For your problem think of iterating through your string. Start with that. Then you need to decide if the currently selected character is part of the alphabet or not. You can do this numerous different ways. Checking ASCII values? Comparing against a string of the alphabet? Once you decide if it is a letter, then you need to rebuild the new string with that letter plus the valid letters before and after that you found or will find. Finally you need to display your new string.
If you look at an ascii table, you can see that A-Z is between 65-90 and a-z is between 97-122.
So, assuming that you only need to remove those characters (not accentuated), and not other characters from other languages for example, not represented in ascii, all you would need to do is loop the string, verify if each char is in these values and remove it.
I have a program set up already to read in a file and split each line into words, storing them into a double vector of strings. That is,
std::vector < std::vector <std::string> > words
So, the idea is to use an array from alphabet a-z and using the ASCII values of the letters to get the index and swapping the characters in the strings with the appropriate shifted character. How would I get the value of each character so that I can look it up as an index?
I also want to keep numbers intact, as a shift cipher, I believe, doesn't do anything with numbers in the text to be deciphered. How would I check if the character is an int so I can leave it alone?
If you want the ASCII value, you simply have to cast the value to a int:
int ascii_value = (int)words[i][j][k];
If you want to have a value starting from A or a you can do this:
int letter_value_from_A = (int)(words[i][j][k] - 'A');
int letter_value_from_a = (int)(words[i][j][k] - 'a');
Your char is nothing else than a value. Take this code as example (I am used to program C++11, so this will be a little ugly):
char shiftarray[256] = {0, 0, 0, 0 // Here comes your map //
std::string output;
for(int w=0; w<words.length(); w++)
{
for(int c=0; c<words[w].length(); c++)
{
output.pushback(shiftarry[words[w][c]]);
}
output.push_back(' ');
}
I do not know how to do it in anything other than basic, but very simply get the ascii value of each letter in the string using a loop. As the loop continues add a value to, or subtract a value from the ascii value you just obtained, then convert it back to a letter and append it to a string. This will give you a different character than you had originally. By doing this, you can load and save data that will look like gibberish if anyone tried to view it other than in the program it was written in. The data then becomes a special propriatry document format.
PROBLEM SOLVED: thanks everyone!
I am almost entirely new to C++ so I apologise in advance if the question seems trivial.
I am trying to convert a string of letters to a set of 2 digit numbers where a = 10, b = 11, ..., Y = 34, Z = 35 so that (for example) "abc def" goes to "101112131415". How would I go about doing this? Any help would really be appreciated. Also, I don't mind whether capitalization results in the same number or a different number. Thank you very much in advance. I probably won't need it for a few days but if anyone is feeling particularly nice how would I go about reversing this process? i.e. "101112131415" --> "abcdef" Thanks.
EDIT: This isn't homework, I'm entirely self taught. I have completed this project before in a different language and decided to try C++ to compare the differences and try to learn C++ in the process :)
EDIT: I have roughly what I want, I just need a little bit of help converting this so that it applies to strings, thanks guys.
#include <iostream>
#include <sstream>
#include <string>
int returnVal (char x)
{
return (int) x - 87;
}
int main()
{
char x = 'g';
std::cout << returnVal(x);
}
A portable method is to use a table lookup:
const unsigned int letter_to_value[] =
{10, 11, 12, /*...*/, 35};
// ...
letter = toupper(letter);
const unsigned int index = letter - 'A';
value = letter_to_value[index];
cout << index;
Each character has it's ASCII values. Try converting your characters into ASCII and then manipulate the difference.
Example:
int x = 'a';
cout << x;
will print 97; and
int x = 'a';
cout << x - 87;
will print 10.
Hence, you could write a function like this:
int returnVal(char x)
{
return (int)x - 87;
}
to get the required output.
And your main program could look like:
int main()
{
string s = "abcdef"
for (unsigned int i = 0; i < s.length(); i++)
{
cout << returnVal(s[i]);
}
return 0;
}
This is a simple way to do it, if not messy.
map<char, int> vals; // maps a character to an integer
int g = 1; // if a needs to be 10 then set g = 10
string alphabet = "abcdefghijklmnopqrstuvwxyz";
for(char c : alphabet) { // kooky krazy for loop
vals[c] = g;
g++;
}
What Daniel said, try it out for yourself.
As a starting point though, casting:
int i = (int)string[0] + offset;
will get you your number from character, and: stringstream will be useful too.
How would I go about doing this?
By trying to do something first, and looking for help only if you feel you cannot advance.
That being said, the most obvious solution that comes to mind is based on the fact that characters (i.e. 'a', 'G') are really numbers. Suppose you have the following:
char c = 'a';
You can get the number associated with c by doing:
int n = static_cast<int>(c);
Then, add some offset to 'n':
n += 10;
...and cast it back to a char:
c = static_cast<char>(n);
Note: The above assumes that characters are consecutive, i.e. the number corresponding to 'a' is equal to the one corresponding to 'z' minus the amount of letters between the two. This usually holds, though.
This can work
int Number = 123; // number to be converted to a string
string Result; // string which will contain the result
ostringstream convert; // stream used for the conversion
convert << Number; // insert the textual representation of 'Number' in the characters in the stream
Result = convert.str(); // set 'Result' to the contents of the stream
you should add this headers
#include <sstream>
#include <string>
Many answers will tell you that characters are encoded in ASCII and that you can convert a letter to an index by subtracting 'a'.
This is not proper C++. It is acceptable when your program requirements include a specification that ASCII is in use. However, the C++ standard alone does not require this. There are C++ implementations with other character sets.
In the absence of knowledge that ASCII is in use, you can use translation tables:
#include <limits.h>
// Define a table to translate from characters to desired codes:
static unsigned int Translate[UCHAR_MAX] =
{
['a'] = 10,
['b'] = 11,
…
};
Then you may translate characters to numbers by looking them up in the table:
unsigned char x = something;
int result = Translate[x];
Once you have the translation, you could print it as two digits using printf("%02d", result);.
Translating in the other direction requires reading two characters, converting them to a number (interpreting them as decimal), and performing a similar translation. You might have a different translation table set up for this reverse translation.
Just do this !
(s[i] - 'A' + 1)
Basically we are converting a char to number by subtracting it by A and then adding 1 to match the number and letters
This is for homework! But I need help anyway. The assignment is to input a sentence then output the number of words, and the number of occurrences of each letter. The output must have the letters in alphabetical order. So far, I've been able to count the number of words and get all the letters to lower case so that I'll be able to keep count of them. My question is how to actually keep count of the letters.
Example of output:
I say Hi.
3 words
1 a
1 h
2 i
1 s
1 y
Here's the code that I have so far:
#include <iostream>
#include <string>
#include <cctype>
using namespace std;
int main()
{
int letters[26];
char letter;
int word = 0;
cout << "Please enter a sentence: "<< endl;
do
{
cin.get(letter);
if(isspace(letter))
word++;
letter = tolower(letter);
cout << letter;
}
while (letter != '\n');
cout << "The number of words = " << word << endl;
return 0;
}
Should I input directly into a C-string? or will that mess up the word count?
If you're allowed to use STL, use std::map for mapping letters to counters. It will additionally sort the letters.
Otherwise, treat chars as indexes in an array of counters and increment them.
My question is how to actually keep
count of the letters
It's fairly straight forward. Simply create an array of 26 integers, (one for each letter), and initialize it to zero.
int letters[26] = { 0 }; // Initialize array to zero
Each value in the array corresponds to a count of a particular letter. Array index 0 refers to 'a', array index 1 refers to 'b', and so on. Then, everytime you encounter a letter, increment the appropriate value in the array. You can use the character 'a' (ASCII value 97) as a starting offset. So, given the variable char letter; you would do:
++letters[tolower(letter) - 'a'];
But always make sure that before you increment the appropriate value in the array, you check that isalpha(letter) && islower(letter) to make sure that your letter is in the range of lowercase a-z; otherwise you will access an index beyond the bounds of the array. You can also test for this condition by saying if (letter >= 'a' && letter <= 'z').
Hint: tolower(letter)-'a' is:
0 if letter is a
1 if letter is b
...
Hm, just few points to make your home task more useful to you (and your code more correct):
Think what happens if you have file with several spaces in a row (word counting).
Think how to be more correct with 'letters' (check for isalpha() at least). Also isalpha() could be key for simpler counting with fixed array [256] (this might be even the best solution as for performance vs std::map usage, check std::map documentation anyway).
Think about more effective file input. At least line at once.