넣으면서 연결하는 이중연결 리스트

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct Animal{
 char name[20];
 double nValue;
 struct Animal *pre;
 struct Animal *next;
};

struct List {
 int length;
 struct Animal* first;
 struct Animal* last;
};

void initList(struct List*);
void add(struct List*, struct Animal*);
void addInIndex(struct List *, struct Animal *, int);
struct Animal* makeAnimal(char*);
struct Animal* getNodeAt(struct List*, int);
double setWeight(struct Animal*);
void displayList(struct List*, int, int);

void initList(struct List* list){
 list->first = NULL;
 list->length = 0;
}

void add(struct List *list, struct Animal *animal){
 int i;
 if(list->length == 0){
  list->first = animal;
  list->last = animal;
 }
 else{
  for(i = 0 ; i < list->length ; i++){
   if(getNodeAt(list, i)->nValue > animal->nValue){
    addInIndex(list, animal, i);
    break;
   }
  }
 }
 list->length++;
}
void addInIndex(struct List *list, struct Animal *animal, int index){
 struct Animal *preAni;
 struct Animal *curAni;
 if(index < 0 || index > list->length){
  index = 0;
 }
 if(index == list->length){
  add(list, animal);
 }
 else if(index == 0){
  curAni = list->first;
  curAni->pre = animal;
  list->first = animal;
  animal->next = curAni;
 }
 else{
  preAni = getNodeAt(list, index - 1);
  preAni->next = animal;
  curAni = getNodeAt(list, index);
  curAni->pre = animal;
  animal->pre = preAni;
  animal->next = curAni;
 }
}

struct Animal* makeAnimal(char* name){
 struct Animal *newAnimal = (struct Animal*) malloc(sizeof(struct Animal));
 strcpy(newAnimal->name,name);
 newAnimal->nValue = setWeight(newAnimal);
 return newAnimal;
}

struct Animal* getNodeAt(struct List* list, int index){
 int i;
 struct Animal* current;
 if(index <= list->length /2){
  current = list->first;
  for (i = 0 ; i < index ; i++){
   current = current->next;
  }
 }
 else {
  current = list->last;
  for(i = 1 ; i < list->length - index ; i++){
   current = current->pre;
  }
 }
 return current;
}

double setWeight(struct Animal* animal){
 char letter;
 letter = animal->name[0];
 return letter / 128.0;
}
void displayList(struct List *list, int start, int end){
 int i;
 if(start < 0){
  start = 0;
 }
 if(end >= list->length){
  end = list->length;
 }
 for (i = start ; i < end ; i++){
  printf("%d : %s(%.2f)\n",i , getNodeAt(list, i)->name, getNodeAt(list, i)->nValue);
 }
}

void main(){
 struct List *p_List = (struct List*) malloc(sizeof(struct List));
 initList(p_List);
 add(p_List, makeAnimal("Tiger"));
 add(p_List, makeAnimal("Lion"));
 add(p_List, makeAnimal("Monkey"));
 add(p_List, makeAnimal("Rabbit"));
 add(p_List, makeAnimal("Horse"));
 displayList(p_List, 0, p_List->length);
}

아하하 다했당 ㅎㅎ