對象數組的插入方法C++

Question

我有一個稱爲值的整型數據數組，我需要在數組中插入一個新的Integerdata。我曾考慮過使用臨時數組來複制所有內容，然後創建一個大小爲+ 1的原始數組，但我不斷收到很多錯誤。任何幫助？

class IntegerData : public Data { 
public: 
int value; 

// This is the syntax for a constructor that initializes the 
// properties value to the parameters 
IntegerData(int value) : value(value) {} 

} 
class ArrayCollection : Collection { 
// length of values is always the same as count 
Data ** values; 
int count; 

public: 
ArrayCollection() { 
    // initialize the array to NULL 
    this->values = NULL; 
    this->count = 0; 
} 

~ArrayCollection() { 
    // must clean up the internally allocated array here 
    if (values != NULL) { 
    delete [] values; 
    } 
} 

/** 
* Returns the count of the number of elements in the Collection 
*/ 
int size() const { 
    return count; 
} 



    /** 
* Gets the Data value at the specified index. If index >= size() then 
* NULL is returned. 
*/ 
Data * get(int index) { 
    if (index >= size()) { 
    return NULL; 
    } 
    else { 
    return values[index]; 
    } 
} 



????-- I need help with this method-- 
// I try to dynamically allocate tempArray but I get the error message saying: cannot 
// allocate an object of abstract type 'Data' 
void insert(Data * other){ 
count++; 
Data **tempArray = new Data[count]; 

for(int i = 0; i < count; i++){ 

tempArray[i] = values[i]; 
} 

delete [] values; 



    values = tempArray; 

} 




} 






int main(int argc, const char * argv[]) { 
// create an ArrayCollection for our collection of integers 
ArrayCollection * collection = new ArrayCollection(); 

if (argc == 1) { 
// they didn't provide any arguments to the program, insert a 
// value of zero so that the main function still works 
collection->insert(new IntegerData(0)); 
} 
else { 
for (int i = 1; i < argc; i++) { 
    // read user input for integer value 
    int x = atoi(argv[i]); 

    // insert it to our collection 
    collection->insert(new IntegerData(x)); 
} 
} 

// print the collection 
cout << collection->toString() << endl; 

// check the implementation of member 
IntegerData * five = new IntegerData(5); 
cout << "five is a member of collection? " << collection->member(five) << endl; 

// now we are going to insert and remove a few items -- MARKER (a) 
IntegerData * v0 = (IntegerData *)collection->get(0); 
collection->remove(v0); 
cout << collection->toString() << endl; 

// check after removing the 0th element -- MARKER (b) 
cout << "five is a member of collection? " << collection->member(five) << endl; 

collection->insert(v0); 
cout << collection->toString() << endl; 

// check after inserting the 0th element back 
cout << "five is a member of collection? " << collection->member(five) << endl; 

// clean up memory 
delete five; 

// must delete IntegerData instances that we allocated in main 
// because they are not deleted by the data structure 
for (int i = 0; i < collection->size(); i++) { 
delete collection->get(i); 
} 
// now delete the data structure -- MARKER (c) 
delete collection; 
} 

Answer 1

由於您使用C++我會建議使用矢量來代替：

std::vector<Data *> vect; 
... 
void insert(Data * other){ 
    vect.push_back(other); 
} 

否則，在C，該功能可這樣的表現：

（假設你的方式分配values陣列首先不允許動態調整大小......）

• 創建一個新的te大小（計數++）的mporary陣列values_tmp
• 然後使用memcpy到先前數據複製到新的數組
• 存儲的值：values_tmp[count] = other;末。
• 釋放內存爲values
• 擦除values新的數組：values = values_tmp;

Answer 2

你的價值觀數組的初始化是不是從你提供的代碼示例顯而易見的，但是，我會盡力給你一些建議：

如果有使用此數組（沒有STL容器），那麼你或許應該把它初始化爲一些中等規模的價值，說這個數字的128跟蹤，而且跟蹤的其中的項目數量（int coun T）。

當你的數組變滿時，你將不得不調整大小。創建一個大小爲256（這是原始大小的兩倍）的新數組，複製舊數組中的元素，然後刪除舊數組。

通過這種方式，您可以以對數速率調整大小，因此插入時間可以攤銷。

（是的，這是從什麼STL的vector沒有......如果我們不能使用它，爲什麼不模仿什麼時間？）

Answer 3

這絕對可能不是最有效的方式，但你可以只需用新增的大小創建一個新的數組，循環遍歷並複製每個元素，直到到達插入索引，然後複製插入的元素，然後繼續複製其餘元素並返回新數組。

IntegerData* insert(Data *other, int index) 
{ 
    IntegerData *newArray = new IntegerData[count +1]; 
    int offset = 0; 
    for(int i=0;i<count+1;i++) 
    { 
    if (i == index) 
    { 
     newArray[i] = other; 
     offset = 1; 
    } 
    else 
    { 
     newArray[i] = oldArray[i-offset]; 
    } 
    } 
    return newArray; 
}