CODEWITHSUNDEEP
c++arrays
user3517150
user3517150

Reputation: 33

How to fill an array with one character in C++

Instead of setting up a loop to go through each position of this array and set it equal to this dot

int arraySize=50;
char board[arraySize];

     for(i=0; i<arraySize; i++)
          board[i]='.';

Is there any way I can declare an array to be filled with these '.' right away?

e.g. char board[arraySize]={'.'};

Upvotes: 3

Views: 12167

Answers (6)

usr1234567
usr1234567

Reputation: 23324

Use std::array instead, then you can use fill.

#include <array>
[..]
std::array<char, 50> board;
board.fill('.');

But be aware, this is C++11 and internally there is a loop over your array, too. You get less and cleaner code, but it isn't faster.

Upvotes: 1

4pie0
4pie0

Reputation: 29724

std::vector is a C++ way to deal with array which size can be changed at run time:

std::vector<char> v( 50, '.'); // a vector with 50 dots

http://en.cppreference.com/w/cpp/container/vector

Upvotes: 0

feeling_lonely
feeling_lonely

Reputation: 6853

The issue with that declaration is that you allocate memory at compile time using a size that is known only at run time. arraySize may change at anytime. If you say for example:

#define ARRAY_SIZE 50
char board[ARRAY_SIZE];

This way the size to be allocate is known at compile time and the compiler wont complain. Then you can initialize using: memset(array, '.', size_of_array);

Another option you allocate at runtime using new and use "value initialization" like this: 

char * board = new char[arraySize]();

This will allocate AND initialize the array for you at runtime.

Upvotes: 1

Mr.C64
Mr.C64

Reputation: 42964

An option you have is to use std::vector, and specify the initial "fill" value in the proper constructor overload:

#include <vector> // For std::vector
....
std::vector<char> board(arraySize, '.');

If you really need a raw C array, you can always use std::fill() to simply fill it with some value:

#include <algorithm> // For std::fill
#include <iterator>  // For non-member std::begin and std::end 
....
static const int arraySize = 50;
char board[arraySize];
fill(begin(board), end(board), '.');

Another option is to use std::array (which is lightweight and zero-overhead like a raw C array, but offers a C++ STL interface too):

#include <algorithm> // For std::fill
#include <array>     // For std::array
....

static const int arraySize = 50;
std::array<char, arraySize> board;
std::fill(board.begin(), board.end(), '.');

// or just:
// board.fill('.');
// Since std::array has a fill() method.

(Frankly, in C++, I think that if you really need to use a statically-sized fixed-size array, std::array is better than raw C arrays.)

Upvotes: 0

Phillip Ngan
Phillip Ngan

Reputation: 16106

Instead of an array, you could construct a vector in this way:

vector<char> board(arraySize, '.');

Vectors can then be used like an array:

char c = board[1];

Upvotes: 4

jordanbana
jordanbana

Reputation: 97

As far as i know, the only way to achieve that would be to actually do what you posted char board[arraySize]={'.', '.','.'......(50 times)}, but actually copy and paste that '.' 50 times, which is a hassle and not smart. So the for loop works, or using vectors!

Upvotes: 1

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