c++ - 类容量函数不能正常工作

Question

我在 push back 函数中编写了一个容量函数，以返回当前为向量数组分配的存储空间的大小。在插入测试用例的过程中，如下图所示，它没有正常工作（查看容量）。插入工作顺利，但容量无法正常工作，并且以某种方式导致在其末尾转储中止的核心。有人可以向我强调这是为什么吗？谢谢！

输出错误：

********** TestInsert **********
(size=0, capacity=0)
push_back 8 floats:
    0  (size=1, capacity=1)
    0   1.41  (size=2, capacity=2)
    0   1.41   2.82  (size=3, capacity=4)
    0   1.41   2.82   4.24  (size=4, capacity=4)
    0   1.41   2.82   4.24   5.65  (size=5, capacity=8)
    0   1.41   2.82   4.24   5.65   7.06  (size=6, capacity=8)
    0   1.41   2.82   4.24   5.65   7.06   8.47  (size=7, capacity=8)
    0   1.41   2.82   4.24   5.65   7.06   8.47   9.89  (size=8, capacity=8)
insert(3, 99):
    0   1.41   2.82     99   4.24   5.65   7.06   8.47   9.89  (size=9, 
capacity=8)
insert(0, 98):
    98      0   1.41   2.82     99   4.24   5.65   7.06   8.47   9.89  
(size=10, capacity=8)
insert(6, 97):
    98      0   1.41   2.82     99   4.24     97   5.65   7.06   8.47   9.89  (size=11, capacity=8)
Construct from int array:
6  6  16  14  -6  12  6  10  8  6  6  4  2  0  (size=14, capacity=1)
Aborted (core dumped)

正确的输出：

********** TestInsert **********
(size=0, capacity=0)
push_back 8 floats:
    0  (size=1, capacity=1)
    0   1.41  (size=2, capacity=2)
    0   1.41   2.82  (size=3, capacity=4)
    0   1.41   2.82   4.24  (size=4, capacity=4)
    0   1.41   2.82   4.24   5.65  (size=5, capacity=8)
    0   1.41   2.82   4.24   5.65   7.06  (size=6, capacity=8)
    0   1.41   2.82   4.24   5.65   7.06   8.47  (size=7, capacity=8)
    0   1.41   2.82   4.24   5.65   7.06   8.47   9.89  (size=8, capacity=8)
insert(3, 99):
    0   1.41   2.82     99   4.24   5.65   7.06   8.47   9.89  (size=9, 
capacity=16)
insert(0, 98):
    98      0   1.41   2.82     99   4.24   5.65   7.06   8.47   9.89  
(size=10, capacity=16)
insert(6, 97):
    98      0   1.41   2.82     99   4.24     97   5.65   7.06   8.47   9.89  
(size=11, capacity=16)
Construct from int array:
6  6  16  14  -6  12  6  10  8  6  6  4  2  0  (size=14, capacity=16)

头文件：

template <typename T>
class vec
{

private:
T* v;
int count; //size
int capacity;
public:

vector(){ //default constructor
    capacity=0;
    v = nullptr;
    count = 0;
}

vector(const vector& b) //copy contructor
{
//..
}   

~vector() {//destructor
//..
}

void push_back(const T& t) // contain the capacity 
{
    if(count+1>capacity)
{
    capacity = std::max(2*capacity, 1);

    T* newData = new T[capacity];
    for(int i=0; i <count; i++)
    {
        newData[i] = v[i];
    }
    delete[] v;
    v = newData;
}
v[count++] = t;
}

void insert(int index, T number)
{
    for (int i = count; i >= index; i--) {
        v[i + 1] = v[i];
    }

    count++;
    v[index] = number;
}

template <typename T1>
friend void Print(const vector<T1>& rp); //friend print

friend  void Print(const vector<float>& rp);    
};

template <typename T1>
void Print (const vector<T1>& rp)
{
for (unsigned i = 0; i < rp.size(); i++)
std::cout << rp[i] << "  ";
std::cout << "(size=" << rp.size()<< "," << " " << "capacity=" 
<< rp.capacity << ")"; 
std::cout << std::endl;
}

void Print (const vector<float>& rp)
{   
for (unsigned i = 0; i < rp.size(); i++)
{     
    std::cout << std::setw(5) << std::setprecision(3)
    << float (rp[i]) <<"  ";
}    
std::cout << "(size=" << rp.size()<< "," << " " << "capacity=" 
<< rp.capacity << ")"; 
std::cout << std::endl;

}

主文件：

void TestInsert(void)
{
{
cout << "\n********** TestInsert **********\n";
cs150::vector<float> a;
Print(a);

cout << "push_back 8 floats:\n";
for( float i = 0; i < 8; ++i ) 
{
  a.push_back( i * 1.412492f );
  Print(a);
}

cout << "insert(3, 99):\n";
a.insert(3, 99);
Print(a);

cout << "insert(0, 98):\n";
a.insert(0, 98);
Print(a);

cout << "insert(6, 97):\n";
a.insert(6, 97);
Print(a);
}
{
int ia[] = { 
  2, 4, 6, 6, 8, 10, 6, 12, -6, 14, 16, 6, 6 
};

std::size_t size = sizeof( ia ) / sizeof( *ia );

std::cout << "Construct from int array:\n";
cs150::vector<int> a;

a.push_back( 0 );

for( std::size_t i = 0; i < size; ++i )
  a.insert( 0, ia[i] );

Print(a);
}
}

int main( int argc, char **argv )
{
std::size_t test_num = 0;

if( argc > 1 )
    test_num = std::size_t( std::atoi( argv[ 1 ] ) );

typedef void (*Test)( void );

Test Tests[] = {

TestInsert,             //  4

};

std::size_t num = sizeof( Tests ) / sizeof( *Tests );

if( test_num == 0 ) 
{
    for( std::size_t i = 0; i < num; ++i )
  Tests[ i ]();
} 
else if( test_num <= num )
{
    Tests[ test_num - 1 ]();
}

return 0;
}

标签： c++functioninsert