c++基础知识

1 

在c++中是不允许数组作为函数的返回值的 

int [] someFunction( ); //ILLEGAL 

要想实现函数返回一个数组，那返回对应数组里面类型的指针

you must return a pointer to the array base type and have the pointer point to the array. So, the function declaration would be as follows: 
 int* someFunction( ); //Legal

int* doubler( int a[], int size)
{
int* temp = new int[size];
for ( int i =0; i < size; i++)
 temp[i] = 2*a[i];
 return temp;
 }

调用

int a[] = {1, 2, 3, 4, 5};
int* b;
b = doubler(a, 5);

delete[] b

2 初始化数组的时候必须指定大小

test.cpp:425:23: error: expression in new-declarator must have integral or enumeration type

    char *p =new char[num1+leng2];