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cv5/a_train.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "a_train.h"
+
+
+struct car *add_car(struct car *first, const char *target)
+{
+    struct car *curr_car = (struct car*) calloc(1, sizeof(struct car));
+    strcpy(curr_car -> value, target);
+    curr_car -> next = NULL;
+    if (first == NULL)
+    {
+        // create list if necessary
+        return curr_car;
+    }
+    // add car to the end
+    struct car *prev_car = first;
+    while (prev_car -> next != NULL)
+    {
+        prev_car = prev_car -> next;
+    }
+    prev_car -> next = curr_car;
+    return first;
+}
+
+
+void print_train(struct car *first)
+{
+    struct car *curr_car = first;
+    while (curr_car != NULL)
+    {
+        printf("%s\n", curr_car -> value);
+        curr_car = curr_car -> next;
+    }
+}
+
+
+void cancel_train(struct car *first)
+{
+    if (first == NULL)
+    {
+        return;
+    }
+    cancel_train(first->next);
+    free(first);
+}
+
+
+struct car *clear_train(struct car *first, const char *target)
+{
+    if (first == NULL)
+    {
+        return NULL;
+    }
+    if (strcmp(first -> value, target) == 0)
+    {
+        struct car *answer = first -> next;
+        free(first);
+        return answer;
+    }
+
+    struct car *prev_car = first;
+    struct car *curr_car = first -> next;
+    if (prev_car == NULL)
+    {
+        return first;
+    }
+    while ((prev_car -> next) != NULL) {
+        curr_car = prev_car -> next;
+        if(curr_car == NULL)
+        {
+            break;
+        }
+        // if found target
+        if (strcmp(curr_car -> value, target) == 0)
+        {
+            // remove it and continue
+            struct car *next_car = curr_car -> next;
+            free(curr_car);
+            prev_car -> next = next_car;
+            prev_car = next_car;
+        }
+        else
+        {
+            prev_car = curr_car;
+        }
+        if (prev_car == NULL)
+        {
+            break;
+        }
+    }
+    return first;
+}