diff --git a/list/list.c b/list/list.c
index 6ec8597..7a7a4c4 100644
--- a/list/list.c
+++ b/list/list.c
@@ -8,19 +8,26 @@
 
 int main(int argc, char **argv){	
 	rand_init();
+	safeMode(1);
 	List *t_list = init_list();
 	
 	for(int i = 0; i < 9; i++){
 		Node *t_node = init_node();
 		int *t_i = (int *)malloc(sizeof(int));
 		*t_i = i;
-		init_value(t_node,(void *)t_i);
+		init_value(t_node,"int",(void *)t_i);
 		insertInTail(t_list,t_node);
 	}
+	
+	/*Node *t_node = init_node();
+	insertInTail(t_list,t_node);
+	init_value(t_node,(void *)"there");*/
+	
 	int *f_i = (int *)malloc(sizeof(int));
 	*f_i = 3;
+	char *f_s = "there";
 	Node *f_node = findByValue(t_list,"int",(void *)f_i);
-	releaseList(t_list);
-		
+	releaseAll();
+	
 	return 0;
 }
diff --git a/list/list.h b/list/list.h
index 1eb98bb..43b7d5e 100644
--- a/list/list.h
+++ b/list/list.h
@@ -7,6 +7,7 @@ typedef struct Node{
 	unsigned long long id;
 	void *value;
 	int if_setvalue;
+	const char *type;
 	struct Node *next;
 	struct Node *last;
 }Node;
@@ -21,7 +22,7 @@ int safeMode(int ifon);//Safe mode is used to make sure that all malloced will b
 int releaseAll(void);
 List *init_list(void);
 Node *init_node(void);
-int init_value(Node *,void *);
+int init_value(Node *,const char *,void *);
 void init_rand(void);
 
 unsigned long long getId(void);
@@ -88,14 +89,15 @@ List *init_list(void){
 	p_list->tail = NULL;
 	if(if_safeMode){
 		Node *p_node = init_node();
-		init_value(p_node,(void *)p_list);
+		init_value(p_node,"pointer",(void *)p_list);
 		insertInTail(list_list,p_node);
 	}
 	return p_list;
 }
 
-int init_value(Node *p_node,void * p_value){
+int init_value(Node *p_node,const char *type,void * p_value){
 	p_node->if_setvalue = 1;
+	p_node->type = type;
 	p_node->value = p_value;
 	return 0;
 }
@@ -150,7 +152,10 @@ int releaseNode(Node *p_node){
 	}
 	if(p_node->if_setvalue == 1){
 		free(p_node->value);
+		p_node->value = NULL;
 	}
+	p_node->last = NULL;
+	p_node->next = NULL;
 	free(p_node);
 	return 0;
 }
@@ -159,18 +164,27 @@ int releaseList(List *p_list){
 	Node *p_node, *pl_node;
 	p_node = p_list->head;
 	if(if_safeMode == 1){
-		Node *tar_list = findByValue(list_list,"int",(void *)p_list);
+		Node *tar_list = findByValue(list_list,"pointer",(void *)p_list);//turn pointer in to int to compare.
 		removeByNode(list_list,tar_list);
 	}
 	while (p_node != NULL){
 		pl_node = p_node;
 		p_node = p_node->next;
+		pl_node->next = NULL;
+		pl_node->last = NULL;
 		releaseNode(pl_node);
 	}
+	p_list->head = NULL;
+	p_list->tail = NULL;
+	p_list->length = 0;
 	free(p_list);
 	return 0;
 }
 
+unsigned long long len(List *p_list){
+	return p_list->length;
+}
+
 int removeById(List *p_list, unsigned long id){
 	Node *tmp = p_list->head;
 	if( isListEmpty(p_list) )
@@ -179,7 +193,8 @@ int removeById(List *p_list, unsigned long id){
 		if(tmp->id == id) {
 			tmp->last->next = tmp->next;
 			tmp->next->last = tmp->last;
-			releaseNode(tmp);
+			//releaseNode(tmp); not necessary
+			p_list->length -= 1;
 			return 1;//found
 		}
 		else{
@@ -198,7 +213,8 @@ int removeByNode(List *p_list, Node *p_node){
 		if(tmp == p_node){
 			tmp->last->next = tmp->next;
 			tmp->next->last = tmp->last;
-			releaseNode(tmp);
+			//releaseNode(tmp); not necessary
+			p_list->length -= 1;
 			return 1;//found
 		}
 		else{
@@ -213,10 +229,11 @@ int popFromHead(List *p_list){
 	if( isListEmpty(p_list) )
 		return -1;
 	else{
-		Node *tmp = p_list->head;
+		//Node *tmp = p_list->head;
 		p_list->head->next->last = NULL;
 		p_list->head = p_list->head->next;
-		releaseNode(tmp);
+		//releaseNode(tmp); not necessary
+		p_list->length -= 1;
 	}
 
 	if( isListEmpty(p_list) ){
@@ -230,10 +247,11 @@ int popFromTail(List *p_list){
 	if( isListEmpty(p_list) )
 		return -1;
 	else{
-		Node *tmp = p_list->tail;
+		//Node *tmp = p_list->tail;
 		p_list->tail->last->next = NULL;
 		p_list->tail = p_list->tail->last;
-		releaseNode(tmp);
+		//releaseNode(tmp); not necessary
+		p_list->length -= 1;
 	}
 
 	if( isListEmpty(p_list) ){
@@ -275,6 +293,7 @@ Node *findById(List *p_list, const unsigned long long id){
 Node *findByValue(List *p_list, const char *type, const void *value){
 	Node *p_node = p_list->head;
 	while(p_node != NULL){
+		if(strcmp(p_node->type,type)) continue;//continue when type is not the same.
 		if(!strcmp(type,"int")){
 			if(*((int *)p_node->value) == *((int *)value)){
 				return p_node;
@@ -291,6 +310,11 @@ Node *findByValue(List *p_list, const char *type, const void *value){
 				return p_node;
 			}
 		}
+		else if(!strcmp(type,"pointer")){
+			if(p_node->value == value){
+				return p_node;
+			}
+		}
 		
 		p_node = p_node->next;