Sum via pointer walking

Challenge

Sum a slice of an int array described by a begin/end pointer pair (like C++ iterators).

Task

Implement long sum_walk(const int *begin, const int *end) that returns the sum of the ints in the half-open range [begin, end). No main — the grader calls it.

Input

Two pointers into the same array: begin (inclusive) and end (exclusive). The range may be empty (begin == end).

Output

The sum of the elements from begin up to but not including end, as a long.

Example

sum_walk(a, a+5)   where a={1,2,3,4,5}   ->   15
sum_walk(a, a)                            ->   0
sum_walk(a+1, a+4) where a={1,2,3,4,5}   ->   9

Edge cases

• begin == end: the range is empty, return 0.

Rules

• Walk with pointer arithmetic; do not take a separate length parameter.

Why this matters

Transfer exercise: apply the lesson to a complete function contract.

Input format

Two pointers into the same array: begin (inclusive) and end (exclusive). The range may be empty (begin == end).

Output format

The sum of the elements from begin up to but not including end, as a long.

Constraints

Live same-array begin/end with begin <= end, including one-past end; each partial sum fits long. Read only.

Starter code

#include <stddef.h>

long sum_walk(const int *begin, const int *end) {
    /* TODO */
    return 0;
}

Common mistakes

Reading end or treating the range as inclusive.

Edge cases to handle

Empty half-open range; subrange; mixed signs; exclude the end element.