Insert Sort on Lined List

insert_sort.c

#include "insert_sort.h"

Node* find_node(int value)
{
    Node *start = &root;

	while(start->after != NULL) {
		if(start->value == value)
			return start;
		else
			start = start->after;
	}

	return NULL;
}


Node* insert_node(int value)
{
	Node *start = &root;

	Node *need = (Node *)malloc(sizeof(Node));
	need->value = value;
	need->after = NULL;
	need->pre = NULL;

	while(start->after != NULL) {
		if(start->value <= value)
			start  = start->after;
		else {
			break;
		}
//		else {
//
//			start->pre->after = need;
//			need->pre = start->pre;
//			need->after = start;
//			start->pre = need;
//			return need;
//		}
	}

//	if(start->after == NULL) {
//		if(start->value <= value) {
//			start->after = need;
//			need->pre = start;
//		}
//		else {
//			start->pre->after = need;
//			need->pre = start->pre;
//			need->after = start;
//			start->pre = need;
//		}
//	}

	if(start->after == NULL && start->value <= value) {
		start->after = need;
		need->pre = start;
	}
	else {
					start->pre->after = need;
					need->pre = start->pre;
					need->after = start;
					start->pre = need;
	}

	return need;
}



//int main(void)
//{
//	int needs[10] = {1,3,1,6,7,8,2,10,9,4};
//	int i;
//
//	for(i = 0; i < 10; i++) {
//		insert_node(needs[i]);
//	}
//
//	Node *p = &root;
//
//	while(p != NULL) {
//		printf("NODE VAL: %d\n",p->value);
//		p = p->after;
//	}
//
//	return 0;
//}

insert_sort.h

#include <stdio.h>

typedef struct node {
    struct node *pre, *after;
	int value;
} Node;

Node root = {NULL, NULL, '\0'};


Node* insert_node(int value);

Node* find_node(int value);