C指向指针的指针的问题，非常感谢！！！

[我是小贺]

#include <iostream>
using namespace std;
void main()
{
char** str = new char*[3];
str[0] = new char[20];
str[1] = new char[20];
str[2] = new char[20];
str[0] = "Nihao";
str[1] = "NihaoMa";
str[2] = "NihaoYa";
int i;
for(i=0; i<3; i++)
cout<<str[i]<<endl;
char** str1 = new char*[2];
str1[0] = str[0];
str1[1] = str[2];
for(i=0; i<2; i++)
cout<<str1[i]<<endl;
// delete str[1];
delete [] str;
str = str1;
/* for(i=0; i<2; i++)
delete str[i];*/
delete []str;
}
上面代码可以运行，
但是，一旦将两个注释处的其中任意一处去掉，将会出现问题，

VC++弹出一个对话框，显示如下：

Debug Assertion Failed!

Program: ...\数据库实验\NewDBS\Debug\MYDBS.exe
File: dbgheap.c
Line: 1044

Expression: _CrtIsValidHeapPointer(pUserData)

For information on how your program can cause assertion
failure, see the Visual C++ documentation on asserts.

(Press Retry to debug the application)

麻烦各位帮我看看这是怎么一回事？

[太乙]

#include <iostream> 
using namespace std; 
void main() 
{ 
	char** str = new char*[3]; 
	str[0] = new char[20]; 
	str[1] = new char[20]; 
	str[2] = new char[20]; 
	strcpy(str[0] , "Nihao"); 
	strcpy(str[1] , "NihaoMa"); 
	strcpy(str[2] , "NihaoYa"); 
	int i; 
	for(i=0; i <3; i++) 
		cout <<str[i] <<endl; 
	char** str1 = new char*[2]; 
	str1[0] = str[0]; 
	str1[1] = str[2]; 
	for(i=0; i <2; i++) 
		cout <<str1[i] <<endl; 
	// delete str[1];
	
	delete[] str[0];
	delete[] str[1];
	delete[] str[2];

	delete[] str1;
	
	delete [] str; 

} 

[太乙]

    strcpy(str[0] , "Nihao"); 
    strcpy(str[1] , "NihaoMa"); 
    strcpy(str[2] , "NihaoYa"); 

如果像lz那样，那么就是将str[0]指向了常量指针！肯定不对！

[机智的呆呆]

#include <iostream> 
using namespace std; 
void main() 
{ 
    char** str = new char*[3]; 
    str[0] = new char[20]; 
    str[1] = new char[20]; 
    str[2] = new char[20]; 
    str[0] = "Nihao"; //内存泄漏
    str[1] = "NihaoMa";//内存泄漏
    str[2] = "NihaoYa"; //内存泄漏
    int i; 
    for(i=0; i <3; i++) 
    cout <<str[i] <<endl; 
    char** str1 = new char*[2]; 
    str1[0] = str[0]; 
    str1[1] = str[2]; 
    for(i=0; i <2; i++) 
    cout <<str1[i] <<endl; 
    // delete str[1];//此时str[1]已不指向开始new的内存，delete出错
    delete [] str; 
    str = str1; 
    /* for(i=0; i <2; i++) 
    delete str[i];*/ 
    delete []str; 
}