我将如何将该递归函数转换为迭代函数？

Question

我在尝试将此递归函数find_reachable(..)转换为迭代等效项时遇到麻烦。我环顾四周，看到了使用堆栈的建议，但无法弄清楚。我也认识到该函数是尾递归的，但不知道该如何处理。 if声明让我特别难过。任何帮助表示感谢，谢谢。

void find_reachable(struct person *current, int steps_remaining,
                              bool *reachable){
    // mark current root person as reachable
    reachable[person_get_index(current)] = true;
    // now deal with this person's acquaintances
    if (steps_remaining > 0){
        int num_known = person_get_num_known(current);
        for (int i = 0; i < num_known; i++){
            struct person *acquaintance = person_get_acquaintance(current, i);
            find_reachable(acquaintance, steps_remaining - 1, reachable);
        }
    }
}
.....
struct person {
  int person_index; // each person has an index 0..(#people-1)
  struct person ** known_people;
  int number_of_known_people;
};

// return the person's unique index between zero and #people-1
int person_get_index(struct person * p) {
  return p->person_index;
}

// return the number of people known by a person
int person_get_num_known(struct person * p) {
  return p->number_of_known_people;
}

// get the index'th person known by p
struct person * person_get_acquaintance(struct person * p, int index) {
  //fprintf(stderr, "index %d, num_known %d\n", index, p->number_of_known_people);
  assert( (index >= 0) && (index < p->number_of_known_people) );
  return p->known_people[index];
}

Answer 1

完全透明，我不太了解c，所以我在不知道语法的地方使用了伪代码，但是类似的东西可能起作用？

void find_reachable(struct person *current, int steps_remaining, bool *reachable){

    stack = /* create a new stack which contains a (person, int) touple or struct */

    stack.push(/* current & steps_remaining*/)

    while (/*stack is not empty*/) {
        currentStruct = /* pop the top of stack */
        current = currentStruct.person
        depth = currentStruct.depth

        reachable[person_get_index(current)] = true;

        if (depth - 1 <= 0) {
            continue;
            // don't add this person's aquantances b/c we're 'steps_remaining' levels in
        }

        int num_known = person_get_num_known(current);
        for (int i = 0; i < num_known; i++){
            struct person *acquaintance = person_get_acquaintance(current, i);
            stack.add(/*acquantance & depth - 1*/)
        }
    }
}

编辑：改进的代码