國立暨南國際大學 113 學年度第二學期小考試卷

1. (10%) Determine whether the syntax of the following code is correct or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   //  Reading/writing a binary file
   #include <iostream>
   int main()
   {
       const char s[4][3] = { "12", "34", "56", "78" };
       char t[2][6];
       FILE* fp = fopen("a.txt", "wb");
       fwrite(s, 3, 4, fp);
       fclose(fp);
       fp = fopen("a.txt", "rb");
       fread(t, 6, 2, fp);
       fclose(fp);
       t[1][2] = 65;       // 'A' == 65
       std::cout << t[0] << std::endl << t[1] << std::endl;
       return 0;
   }
   
2. (10%) Assume there is no run-time error (e.g., out of memory).  Predict the output the following program.
   // Linked-list as a queue
   #include <iostream>
   struct Node {
       int value;
       Node* pNext;
   };
   
   Node* front = nullptr;  // a global variable
   void enqueue(int v) {
       Node* p = new Node;
       p->value = v;
       p->pNext = nullptr;
       if (front == nullptr) {
           front = p;
       } else {
           Node* rear = front;
           while (rear->pNext != nullptr)
               rear = rear->pNext;
           rear->pNext = p;
       }
   }
   
   int dequeue() {
       Node* p = front;
       int result = front->value;
       front = front->pNext;
       delete p;
       return result;
   }
   
   void display() {
       Node* p = front;
       while (p) {
           std::cout << p->value << ' ';
           p = p->pNext;
       }
       std::cout << std::endl;
   }
   
   int main() {
       enqueue(1); enqueue(3); enqueue(5);
       display();
       enqueue(2); enqueue(4);
       std::cout << dequeue() << dequeue();
       display();
       return 0;
   }
   
3. (10%)Predict the output of the following program, and draw a figure of the created binary tree.
   // insertToTree
   #include <iostream>
   struct Node {
      int value;
      Node* left;
      Node* right;
   };
   
   void printTree(Node* p) {
      if (p) {
          printTree(p->left);              // recursive function call
          std::cout << p->value;
          printTree(p->right);
      }
   }
   
   void insertToTree(Node*& p, int v) {    // A pointer passed by ref
       if (p == nullptr) {
           p = new Node;
           p->value = v;
           p->left  = nullptr;
           p->right = nullptr;
       } else if (v < p->value)
           insertToTree(p->right, v);       // recursive function call
       else
           insertToTree(p->left, v);  
   }
   
   int main() {
       Node* root = nullptr;
       insertToTree(root, 3);
       insertToTree(root, 1);
       insertToTree(root, 2);
       insertToTree(root, 5);
       insertToTree(root, 4);
       printTree(root);
       std::cout << std::endl;
       return 0;
   }