[英]How to reference a dynamically allocated character array in c++
我需要了解如何在c ++中動態分配的字符數組中的各個索引位置中操縱數據。 我正在發出嘎嘎聲(隊列/堆棧)。 我關注的變量是“項目”。
這是Quack的類定義:
class Quack
{
public:
static const char YOUR_NAME[]; // used for printing out programmer's name
static const bool PREMIUM_VERSION; // used to designate Regular vs. Premium
Quack(int capacity, int growBy = 0);
// capacity: # of slots in array
// growBy: # of slots to add to array when it grows, 0 means "don't grow"
~Quack(void);
bool pushFront(const char ch); // push an item onto the front
bool pushBack(const char ch); // push an item onto the back
bool popFront(char& ch); // pop an item off the front
bool popBack(char& ch); // pop an item off the back
void rotate(int r); // "rotate" the stored items (see note below)
void reverse(void); // reverse the order of the stored items
int itemCount(void); // return the current number of stored items
void printArray(std::ostream& out) // print contents of array
{
unsigned int ch;
out << "[ ";
for (int i = 0; i < capacity; i++) {
ch = static_cast<unsigned char>(items[i]); // avoid sign extension
if (ch == '-') // print in hex, because using '-' for 0xCD
goto printHex;
else if (ch >= '!' && ch <= '}') // ASCII text character
out << static_cast<char>(ch) << ' ';
else if (ch == 0xCD) // print 0xCD as '-'
out << "- ";
else // print everything else as hex
goto printHex;
continue;
printHex:
out << std::setw(2) << std::setfill('0') << std::hex << ch << ' ';
}
out << ']' << std::endl;
}
private:
char *items;
int nItems;
int capacity;
int growBy;
int *front;
int *back;
public:
friend std::ostream& operator<<(std::ostream& out, Quack *q);
};
現在,這是Quack構造函數:
Quack::Quack(int capacity, int growBy) :
capacity(capacity),
growBy(growBy),
nItems(0),
items(new char[capacity]),
front(NULL),
back(NULL)
{
}
我知道Quack的每個實例都有一個char變量“ items”,它是指向新字符數組的指針。 我不明白的是如何引用數組中的項目。 例如,如果我要引用新字符數組的索引位置0,我說的是items(0)還是items [0],還是完全不同?
謝謝
如您所正確理解的, items
是一個char數組,每個Quack
實例都有其自己的變量items
。 訪問動態分配的數組和靜態分配的數組是相同的。 它們被分配在連續的內存位置。
char arr[24]; // Allocate 24 bytes in contiguous memory locations in stack
char* arr = new char[24]; //Allocate 24 bytes in contiguous memory locations
// in heap
您可以通過以下任意方式訪問變量:
1. Quack q;
cout << q.items << endl; //Print the char array
cout << q.items[1] << endl; // Print the second index position of items
2. Quack* qptr = new Quack();
cout << q->items << endl; //Print the char array
cout << q->items[1] << endl; // Print the second index position of items
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