我在C中有一个大数组(不是c++，如果这有区别的话)。我想初始化相同值的所有成员。
我发誓我曾经知道一个简单的方法。在我的情况下，我可以使用memset()，但没有一种方法来做到这一点，这是建立在C语法?
当前回答
没有人提到访问初始化数组元素的索引顺序。我的示例代码将为它提供一个说明性示例。
#include <iostream>
void PrintArray(int a[3][3])
{
std::cout << "a11 = " << a[0][0] << "\t\t" << "a12 = " << a[0][1] << "\t\t" << "a13 = " << a[0][2] << std::endl;
std::cout << "a21 = " << a[1][0] << "\t\t" << "a22 = " << a[1][1] << "\t\t" << "a23 = " << a[1][2] << std::endl;
std::cout << "a31 = " << a[2][0] << "\t\t" << "a32 = " << a[2][1] << "\t\t" << "a33 = " << a[2][2] << std::endl;
std::cout << std::endl;
}
int wmain(int argc, wchar_t * argv[])
{
int a1[3][3] = { 11, 12, 13, // The most
21, 22, 23, // basic
31, 32, 33 }; // format.
int a2[][3] = { 11, 12, 13, // The first (outer) dimension
21, 22, 23, // may be omitted. The compiler
31, 32, 33 }; // will automatically deduce it.
int a3[3][3] = { {11, 12, 13}, // The elements of each
{21, 22, 23}, // second (inner) dimension
{31, 32, 33} }; // can be grouped together.
int a4[][3] = { {11, 12, 13}, // Again, the first dimension
{21, 22, 23}, // can be omitted when the
{31, 32, 33} }; // inner elements are grouped.
PrintArray(a1);
PrintArray(a2);
PrintArray(a3);
PrintArray(a4);
// This part shows in which order the elements are stored in the memory.
int * b = (int *) a1; // The output is the same for the all four arrays.
for (int i=0; i<9; i++)
{
std::cout << b[i] << '\t';
}
return 0;
}
输出结果为:
a11 = 11 a12 = 12 a13 = 13
a21 = 21 a22 = 22 a23 = 23
a31 = 31 a32 = 32 a33 = 33
a11 = 11 a12 = 12 a13 = 13
a21 = 21 a22 = 22 a23 = 23
a31 = 31 a32 = 32 a33 = 33
a11 = 11 a12 = 12 a13 = 13
a21 = 21 a22 = 22 a23 = 23
a31 = 31 a32 = 32 a33 = 33
a11 = 11 a12 = 12 a13 = 13
a21 = 21 a22 = 22 a23 = 23
a31 = 31 a32 = 32 a33 = 33
11 12 13 21 22 23 31 32 33
其他回答
略带开玩笑的回答;写语句
array = initial_value
用你最喜欢的支持数组的语言(我的是Fortran，但还有很多其他语言)，并将它链接到你的C代码。你可能想把它包装成一个外部函数。
我知道用户Tarski以类似的方式回答了这个问题，但我添加了更多细节。请原谅我的一些C语言，因为我对它有点生疏，因为我更倾向于使用c++，但它就在这里。
如果你提前知道数组的大小……
#include <stdio.h>
typedef const unsigned int cUINT;
typedef unsigned int UINT;
cUINT size = 10;
cUINT initVal = 5;
void arrayInitializer( UINT* myArray, cUINT size, cUINT initVal );
void printArray( UINT* myArray );
int main() {
UINT myArray[size];
/* Not initialized during declaration but can be
initialized using a function for the appropriate TYPE*/
arrayInitializer( myArray, size, initVal );
printArray( myArray );
return 0;
}
void arrayInitializer( UINT* myArray, cUINT size, cUINT initVal ) {
for ( UINT n = 0; n < size; n++ ) {
myArray[n] = initVal;
}
}
void printArray( UINT* myArray ) {
printf( "myArray = { " );
for ( UINT n = 0; n < size; n++ ) {
printf( "%u", myArray[n] );
if ( n < size-1 )
printf( ", " );
}
printf( " }\n" );
}
上面有一些注意事项;一个是UINT myArray[size];声明时不会直接初始化，但是下一个代码块或函数调用确实会将数组的每个元素初始化为所需的相同值。另一个注意事项是，您必须为将要支持的每种类型编写初始化函数，并且还必须修改printArray()函数以支持这些类型。
您可以使用这里找到的在线编译器尝试此代码。
在过去(我并不是说这是个好主意)，我们设置了第一个元素，然后:
Memcpy (&element [1]， &element [0]， sizeof (element)-sizeof (element [0]);
甚至不确定它是否还能工作(这将取决于memcpy的实现)，但它通过重复地将初始元素复制到下一个元素来工作-甚至对结构数组也有效。
没有人提到访问初始化数组元素的索引顺序。我的示例代码将为它提供一个说明性示例。
#include <iostream>
void PrintArray(int a[3][3])
{
std::cout << "a11 = " << a[0][0] << "\t\t" << "a12 = " << a[0][1] << "\t\t" << "a13 = " << a[0][2] << std::endl;
std::cout << "a21 = " << a[1][0] << "\t\t" << "a22 = " << a[1][1] << "\t\t" << "a23 = " << a[1][2] << std::endl;
std::cout << "a31 = " << a[2][0] << "\t\t" << "a32 = " << a[2][1] << "\t\t" << "a33 = " << a[2][2] << std::endl;
std::cout << std::endl;
}
int wmain(int argc, wchar_t * argv[])
{
int a1[3][3] = { 11, 12, 13, // The most
21, 22, 23, // basic
31, 32, 33 }; // format.
int a2[][3] = { 11, 12, 13, // The first (outer) dimension
21, 22, 23, // may be omitted. The compiler
31, 32, 33 }; // will automatically deduce it.
int a3[3][3] = { {11, 12, 13}, // The elements of each
{21, 22, 23}, // second (inner) dimension
{31, 32, 33} }; // can be grouped together.
int a4[][3] = { {11, 12, 13}, // Again, the first dimension
{21, 22, 23}, // can be omitted when the
{31, 32, 33} }; // inner elements are grouped.
PrintArray(a1);
PrintArray(a2);
PrintArray(a3);
PrintArray(a4);
// This part shows in which order the elements are stored in the memory.
int * b = (int *) a1; // The output is the same for the all four arrays.
for (int i=0; i<9; i++)
{
std::cout << b[i] << '\t';
}
return 0;
}
输出结果为:
a11 = 11 a12 = 12 a13 = 13
a21 = 21 a22 = 22 a23 = 23
a31 = 31 a32 = 32 a33 = 33
a11 = 11 a12 = 12 a13 = 13
a21 = 21 a22 = 22 a23 = 23
a31 = 31 a32 = 32 a33 = 33
a11 = 11 a12 = 12 a13 = 13
a21 = 21 a22 = 22 a23 = 23
a31 = 31 a32 = 32 a33 = 33
a11 = 11 a12 = 12 a13 = 13
a21 = 21 a22 = 22 a23 = 23
a31 = 31 a32 = 32 a33 = 33
11 12 13 21 22 23 31 32 33
方法一:
int a[5] = {3,3,3,3,3};
形式化初始化技术。
方法二:
int a[100] = {0};
但值得注意的是
int a[10] = {1};
不将所有值初始化为1
这种方法只对0进行初始化
如果你这样做
int a[100];
一些编译器倾向于接受垃圾值，因此它总是首选这样做
int a[1000] = {0};
