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Difference between ++*p, *p++ and *++p in c++
In this section we will see what are the differences between *ptr++, *++ptr and ++*ptr in C++.
Here we will see the precedence of postfix++ and prefix++ in C or C++. The precedence of prefix ++ or -- has higher priority than dereference operator ‘*’ and postfix ++ or -- has priority higher than both prefix ++ and dereference operator ‘*’.
When ptr is a pointer, then *ptr++ indicates *(ptr++) and ++*prt refers ++(*ptr)
Example Code
#include<iostream>
using namespace std;
int main() {
char arr[] = "Hello World";
char *ptr = arr;
++*ptr;
cout << *ptr;
return 0;
}Output
I
So here at first ptr is pointing ‘H’. after using ++*ptr it increases H by 1, and now the value is ‘I’.
Example Code (C++)
#include<iostream>
using namespace std;
int main() {
char arr[] = "Hello World";
char *ptr = arr;
*ptr++;
cout << *ptr;
return 0;
}Output
e
So here at first ptr is pointing ‘H’. after using *ptr++ it increases the pointer, so ptr will point to the next element. so the result is ‘e’.
Example Code (C++)
#include<iostream>
using namespace std;
int main() {
char arr[] = "Hello World";
char *ptr = arr;
*++ptr;
cout << *ptr;
return 0;
}Output
e
In this example also we are increasing the ptr using ++, where the precedence of pre-increment ++ is higher, then it increases the pointer first, then taking the value using *. so it is printing ‘e’.
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