Question

我有一个名为values的整数数组，我需要在数组中插入一个新的Integerdata。我已经考虑过制作一个临时数组来复制所有内容，然后创建一个大小为+ 1原始的新数组，但是我一直遇到很多错误。任何帮助？

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

由于您使用的是C ++，我建议使用向量：

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

否则在C中，函数可能表现如下：

（假设您首先分配values数组的方式不允许动态调整大小...）

创建一个大小为（count ++）

values_tmp

然后使用memcpy将以前的数据复制到新数组
将值values_tmp[count] = other;存储在最后。
释放values
使用新阵列删除values：values = values_tmp;

Answer 2

从您提供的代码示例中，您的values数组的初始化并不明显，但是，我会尝试给您一些建议：

如果在这里使用数组（并且没有stl容器），那么你应该把它初始化为一些中等大小的值，比如128.跟踪这个数字，但也要跟踪其中的项目数（int count）。

当你的阵列变满时你将不得不调整大小。创建一个大小为256的新数组（其大小是原始数据的两倍），复制旧数组中的元素，然后删除旧数组。

通过这种方式，您将以对数速率调整大小，因此插入时间可以摊销。

（是的，这取自stl矢量的作用......如果我们不能使用它，为什么不模仿它？）

Answer 3

这绝对可能不是最有效的方法，但你可以创建一个新的增量大小的数组，循环并逐个复制每个元素，直到你到达插入索引，然后复制插入的元素，然后继续复制其余部分并返回新数组。

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;
}

insert对象数组的方法c ++

3 个答案: