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arrayscpost-incrementpre-increment

why doesn't the result of an array member changed when have assigned it?

when I did something like this:

int arr[]={11, 12, 13, 14, 15};
int *p=arr;
*(p++) += 100;

The result of arr[1] was still 12,why?

Solution

  • You are post-incrementing p which does not change p[1]. To change p[1] you need to pre-increment p. And then decrement p to obtain p[1].

    Example: TRY IT ONLINE

    #include <stdio.h>

int main(void){
    int arr[]={11, 12, 13, 14, 15};
    int *p = arr;
    *(++p) += 100;
    p--;
    printf("%d\n", p[1]);
    return 0;
}