cv4

cv4/a_train.c

@@ -6,6 +6,9 @@
 struct car* add_car(struct car* first,const char* target) {
     struct car* newcar = calloc(1,sizeof(struct car));
     strcpy(newcar->value, target);
+     if (first == NULL) {
+        return newcar;
+    }
     struct car* this = first;  
     while (this->next != NULL) {  
         this = this->next;  
@@ -15,21 +18,41 @@ struct car* add_car(struct car* first,const char* target) {
 }
 
 void print_train(struct car* first) {
-    while(first != NULL){
-        printf("%s", first->value);
-        first = first->next;
+    struct car* this = first;
+    while (this != NULL) {
+        printf("%s\n", this->value);
+        this = this->next;
     }
 }
 
 void cancel_train(struct car* first) {
-    while(first != NULL){
-        free(first->next);
-        first = first->next;
+    struct car* this = first;
+    while (this != NULL) {
+        struct car* next_car = this->next;  
+        free(this);                         
+        this = next_car;                    
+   }
+}
+
+
+struct car* clear_train(struct car* first, const char* name) {
+    struct car* this = first;
+    struct car* prev = NULL;
+
+    while (this != NULL) {
+        if (strcmp(this->value, name) == 0) {
+            if (prev == NULL) {
+                struct car* temp = this->next;
+                free(this);
+                return clear_train(temp, name);
+            } else {
+                prev->next = this->next;
+                free(this);
+                return first;
+            }
+        }
+        prev = this;
+        this = this->next;
     }
+    return first;
 }
-
-
-struct car* clear_train(struct car* first, const char* target) {
-	return NULL;
-}
-