C++ 错误：“必须使用大括号括起来的初始化程序初始化数组”

Question

I am getting the following C++ error:

array must be initialized with a brace enclosed initializer 

From this line of C++

int cipher[Array_size][Array_size] = 0;

What is the problem here? What does the error mean? Below is the full code:

string decryption(string todecrypt)
{
    int cipher[Array_size][Array_size] = 0;
    string ciphercode = todecrypt.substr(0,3);
    todecrypt.erase(0,3);
    decodecipher(ciphercode,cipher);
    string decrypted = "";
    while(todecrypt.length()>0)
    {
        string unit_decrypt = todecrypt.substr(0,Array_size);
        todecrypt.erase(0,Array_size);
        int tomultiply[Array_size]=0;
        for(int i = 0; i < Array_size; i++)
        {
            tomultiply[i] = int(unit_encrypt.substr(0,1));
            unit_encrypt.erase(0,1);
        }
        for(int i = 0; i < Array_size; i++)
        {
            int resultchar = 0;
            for(int j = 0; j<Array_size; j++)
            {
                resultchar += tomultiply[j]*cipher[i][j]; 
            }
            decrypted += char((resultchar%229)-26);
        }
    }
    return decrypted;
}

Answer 1

The syntax to statically initialize an array uses curly braces, like this:

int array[10] = { 0 };

This will zero-initialize the array.

For multi-dimensional arrays, you need nested curly braces, like this:

int cipher[Array_size][Array_size]= { { 0 } };

Note that Array_size must be a compile-time constant for this to work. If Array_size is not known at compile-time, you must use dynamic initialization. (Preferably, an std::vector ).

Answer 2

You cannot initialize an array to '0' like that

int cipher[Array_size][Array_size]=0;

You can either initialize all the values in the array as you declare it like this:

// When using different values
int a[3] = {10,20,30};

// When using the same value for all members
int a[3] = {0};

// When using same value for all members in a 2D array
int a[Array_size][Array_size] = { { 0 } };

Or you need to initialize the values after declaration. If you want to initialize all values to 0 for example, you could do something like:

for (int i = 0; i < Array_size; i++ ) {
    a[i] = 0;
}

Answer 3

You can't initialize arrays like this:

int cipher[Array_size][Array_size]=0;

The syntax for 2D arrays is:

int cipher[Array_size][Array_size]={{0}};

Note the curly braces on the right hand side of the initialization statement.

for 1D arrays:

int tomultiply[Array_size]={0};