Question

我正在尝试在C ++中实现向量调整大小功能。我想我处理了每种情况但仍然出现bad_alloc错误。此调整大小实现中的三种情况：1）当new_size小于old_size时（在我的代码中，大小）; 2）当new_size大于但小于容量时; 3）案例3：当新的_size大于容量时

void Vector::resize(int new_size)
{
    //if the new_size is smaller, make the size smaller, don't need to worry about memory
    //the content is reduced to its first n element
    //remove those beyond and destroy them

    if(new_size < size){

        for(int i = size-1; i > new_size; i--){
            erase(i);
        }
        size = new_size;
    }

    //if the new_size is bigger
    //case 1: new_size is smaller than capacity
    //inserting at the end of as many elements as needed
    if(new_size > size && new_size < capacity){

        for(int i=size; i < new_size; i++){
            insert(i, 0.0);
        }
        size = new_size;

    }

    //case 2: new_size is greater than capacity
    //increase the capacity of the container

    //increase the capacity to new_size
    double *tmp_data = new double(new_size);

    //transfer data to tmp_data
    for(int i=0; i < size; i++)
    {
        tmp_data[i] = data[i];
    }

    data = tmp_data;
    delete [] data;

    size = new_size;
    capacity = new_size; 
}

Answer 1

此代码有几个问题。首先跳出的是：

//increase the capacity to new_size
double *tmp_data = new double(new_size);

您打算分配一个数组，但实际上是在分配一个double。你的意思是：

double *tmp_data = new double[new_size];

虽然，一旦你解决了......

data = tmp_data;
delete [] data;

您希望以相反的顺序执行这些操作，否则您将自己留下已删除的成员。

一旦你修复那个，你就想早点return从你的案件中找到。您有三种情况（不是两种，正如您的意见所暗示的那样），并且您只想在您确实需要的情况下重新分配（即情况＃3）。在原样，您将在所有情况下重新分配。

实现向量调整大小功能时出现bad_alloc错误

1 个答案: