add search_before, delete_node; fix traverse_before, delete_node_at

main and test not updated yet

llist.c

@@ -63,6 +63,39 @@ NODE_INT search(NODE *head, datatype data){
 	return curr;
 }
 
+NODE_INT search_before(NODE *head, datatype data, unsigned before){
+//return:
+// node non-null, num>=0 : normal; found data at index[num+before]
+// node NULL, num 0 : head is NULL
+// node NULL, num<0 : found data before enough items processed. num is index.
+//--------------------e.g. search_before({1,2,3},2,3) -> (NULL, -2)
+// node NULL, num>0 : did not find data; returns index of final NULL
+//--------------------e.g. search_before({1,2,3},4,3) -> (NULL, 3)
+	NODE_INT out;
+	out.node = NULL;
+	out.num = 0;
+	if(head==NULL)
+		return out;
+	if(before == 0)
+		return search(head,data);
+	before;
+	NODE **queue = calloc(before, sizeof(NODE*));
+	int i=0;
+	while(head != NULL && head->data != data){
+		queue[i] = head;
+		i = (i+1)%before;
+		out.num++;
+		head = head->next;
+	}
+	if(head == NULL){
+		out.node = NULL;
+		return out;
+	}
+	out.node = queue[i];
+	out.num -= before;
+	return out;
+}
+
 NODE *construct(datatype data, NODE *next){
 //return:
 // pointer to new node : normal
@@ -98,59 +131,39 @@ NODE_INT traverse(NODE *head, int pos){
 	return out;
 }
 
-NODE_INT search_before(NODE *head, datatype data, unsigned before){
+
+//NODE_INT traverse_before(NODE *head, int pos, int offset){
+//	int newPos = pos-offset;
+//	NODE_INT returnCode = traverse(head, newPos);
+//	switch(returnCode.num){
+//		case 0: printf("Case 0-> here is the data: %d\n", returnCode.node->data);
+//			break;
+//		case 1: printf("Case 1-> here is the data: %d\n",returnCode.node->data);
+//			break;
+//		case 2:	printf("Not in the list; returning final data point: %d\n",returnCode.node->data);
+//			break;
+//	}
+//}
+
+NODE_INT traverse_before(NODE *head, int pos, unsigned before){
 //return:
-// node non-null, num>-1: normal; found data at index num+before
-// node NULL, num 0 : head is NULL
-// node NULL, num<0 : completed before enough data processed. num is index.
-//                           e.g. search_before({1,2,3},2,3) -> (NULL, -2)
-// node non-null, num<0 : did not find data; returns node 'before' before last
-//                        if n is index of node returned, num is -(n+1) 
+// 0 : normal
+// 1 : head is null; NODE* return is NULL
+// 2 : reached end of list; NODE* return is final item
+// 3 : reached end of list, but before put result back in list: NODE* is result
+// 4 : before is larger than pos or pos is negative; NODE* return is NULL
+	int effectivePos = pos - before;
 	NODE_INT out;
-	out.node = NULL;
-	out.num = 0;
-	if(head==NULL)
-		return out;
-	if(before == 0)
-		return search(head,data);
-	before;
-	NODE **queue = calloc(before, sizeof(NODE*));
-	int i=0;
-	while(head != NULL && head->data != data){
-		queue[i] = head;
-		i = (i+1)%before;
-		out.num++;
-		head = head->next;
+	out.node=NULL;
+	out.num=4;
+	if(effectivePos >= 0){
+		out = traverse(head, effectivePos);
+		if(out.num==0)
+			out.num = length(out.node) > before ? 0 : 3;
 	}
-	out.node = queue[i];
-	out.num -= before;
-	if(head == NULL)
-		out.num = (-1)-out.num;
 	return out;
 }
 
-NODE_INT traverseBefore(NODE *head, int pos, int offset){
-	int newPos = pos-offset;
-	NODE_INT returnCode = traverse(head, newPos);
-	switch(returnCode.num){
-		case 0: printf("Case 0-> here is the data: %d\n", returnCode.node->data);
-			break;
-		case 1: printf("Case 1-> here is the data: %d\n",returnCode.node->data);
-			break;
-		case 2:	printf("Not in the list; returning final data point: %d\n",returnCode.node->data);
-			break;
-	}
-}
-
-int delete_node_at(NODE *head, int pos){
-	NODE_INT nodeToDelete = traverse(head, pos);
-	NODE_INT priorNode = traverse(head, pos-1);
-	priorNode.node->next = nodeToDelete.node->next;
-	//NODE *nextNode = nodeToDelete.node->next;
-	free(nodeToDelete.node);
-	return 0;
-}
-
 int delete_node_after(NODE *head){
 //return:
 // 0 : normal
@@ -171,6 +184,54 @@ void delete_list(NODE *head){
 	delete_list(tmp);
 }
 
+int delete_node_at(NODE *head, int pos){
+//return:
+// 0 : normal
+// 1 : head is NULL
+// 2 : head->next is NULL: this function will not free head
+// 3 : pos is beyond end of list
+	if(head == NULL)
+		return 1;
+	if(head->next == NULL)
+		return 2;
+	if(pos == 0){
+		head->data = head->next->data;
+		delete_node_after(head);
+		return 0;
+	}
+	NODE_INT priorNode = traverse_before(head, pos, 1);
+	if(priorNode.num == 2 || priorNode.num == 3)
+		return 3;
+	NODE *tmp = priorNode.node->next;
+	priorNode.node->next = tmp->next;
+	free(tmp);
+	return 0;
+}
+
+int delete_node(NODE *head, datatype data){
+//return:
+// 0 : normal
+// 1 : head is NULL
+// 2 : data is sole item in list: this function will not free head
+// -1 : data not found
+	NODE_INT result = search_before(head,data,1);
+	if(result.node == NULL){
+		if(result.num > 0)//not found
+			return -1;
+		if(result.num == 0)//head is null
+			return 1;
+		if(head->next == NULL)//data is sole item in list
+			return 2;
+		//data is first item: preserve address of head while deleting it
+		head->data = head->next->data;
+		delete_node_after(head);
+		return 0;
+	}
+	//data is somewhere in the list
+	delete_node_after(result.node);
+	return 0;
+}
+
 NODE *construct_list(datatype list[], int size){
 //return:
 // pointer to head : normal

llist.h

@@ -20,11 +20,11 @@ NODE_INT search(NODE *head, datatype data);
 NODE_INT search_before(NODE *head, datatype data, unsigned before);
 NODE *construct(datatype data, NODE *next);
 NODE_INT traverse(NODE *head, int pos);
-NODE_INT traverseBefore(NODE *head, int pos, int offset);
+NODE_INT traverse_before(NODE *head, int pos, unsigned before);
 int delete_node_after(NODE *head);
 void delete_list(NODE *head);
 int delete_node_at(NODE *head, int pos);
-//int delete_node(NODE *head, datatype data);
+int delete_node(NODE *head, datatype data);
 NODE *construct_list(datatype list[], int size);
 int add_to_end(NODE *head, datatype new_data);
 int insert_node(NODE *head, int pos, datatype new_data);