C/C ++ -- some development and assignment of pointers

 

I wrote a code today and I always reported an error. It was originally a left-handed Problem of a string, but I was always bored when I reported an error. Then I went online to answer questions from enthusiastic netizens, and I was very enlightened! Haha, now I want to share it with you!

 

 

# Include <iostream>

# Include <cstring>

# Include <malloc. h>

Using namespace std;

Int main ()

{

Char * str = (char *) malloc (20 * sizeof (char); // The first method to open up memory for the pointer

// Char a [20]; // second method for opening up memory for the pointer

// Str =;

// Str = new char [20]; // The third method for opening up memory for the pointer

// Str = "wudemiao"; // The first method for assigning values to pointers

Strcpy (str, "wudemiao"); // assign a second value to the pointer (note the difference)

Cout <strlen (str) <endl;

Cout <str <endl;

Int N = strlen (str );

Int M = 4;

Char ch;

While (M --){

Ch = str [N-1];

For (int I = N-1; I> 0; I --)

{

Str [I] = str [I-1];

}

Str [0] = ch;

 

}

Cout <str <endl;

// Delete str; // do not drop the third method

// The memory will leak when it is lost.

Return 0;

 

}

// What needs to be explained is the above description when we open up memory for pointers

// Among the three methods, remember to use delete str; avoid

// Storage leakage. If str = "wudemiao" is used

// The Pointer Points to a String constant. The 20 strings created in the previous sentence are now

// Access failed, which is a serious problem of Memory leakage. Later

// Use the str pointer to modify the constant of the constant it references. The constant must not be

// Modified, so an error occurs. However, use strcpy (str, "wudemiao ");

// Strcpy () generates a copy, which is an array, natural

// Is a variable, so no matter which method you use to open up the memory for the pointer, if you

// If str = "wudemiao" is used, str points to a word.

// Constant, which cannot be changed in C/C ++.

 

From wudemiao's column