In C, array indexing is formally defined in terms of pointer arithmetic. We CAN create an array by using pointer only.
Note: This program may cause segmentation fault in some systems.
/* Desc: Using only pointer to create variable and array.
some system may not work, because of segmentation fault.
Author: Liutong XU
*/
#include<stdio.h>
int main()
{
int a;
int *p=&a+1; //p point a's neibough
//some system may cause segmentation fault
for (*p=0;*p<10;(*p)++) //*p used as a loop variable
scanf("%d",&p[10+*p]); //p+10~p+19 used as an integer array
for (p[0]=0;p[0]<10;p[0]++) //p[0] is same as *p
printf("%d\t",p[10+p[0]]);
return 0;
}
stdin
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stdout
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Dynaminc Memory Allocation
Segmentation fault normally is caused by invalid pointer reference, because p+20 may violate other variables.
If we have enough valid memory segment for pointer, then no violation will occur.
/* Desc: Dynamic memory allocation
dynamically allocated memory may be used as variable or array,
but with no common names
Author: Liutong XU
*/
#include<stdio.h>
#include<stdlib.h>
int main()
{
int *p;
p = malloc(20); //p points to a 20-byte memory
for (*p=0;*p<10;(*p)++) //*p used as a loop variable
scanf("%d",&p[10+*p]); //p+10~p+19 used as an integer array
for (p[0]=0;p[0]<10;p[0]++) //p[0] is same as *p
printf("%d\t",p[10+p[0]]);
free(p);
return 0;
}
stdin
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stdout
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