PROSAGA码农传奇-C/C++-打印二叉树

<div class =“post-text”itemprop =“text”>
  <P>
    该
     <code>
      insert()
    </code>
     和
     <code>
      createNode()
    </code>
     功能很好。
  </p>
  <P>
    该
     <code>
      inorder()
    </code>
     功能打印
     <code>
      empty
    </code>
     对于树中的每个空指针。然后崩溃，可能是因为它继续尝试递归调用
     <code>
      root->left
    </code>
     即使
     <code>
      root
    </code>
     一片空白。你可能应该在什么时候回来
     <code>
      root
    </code>
     一片空白。
  </p>
  <P>
    仍然很难确定哪个节点与哪个节点相关。也许你应该使用更像这样的代码：
  </p>
   <pre>
    <code>
      #include <stdio.h>
#include <stdlib.h>

struct tree
{
    int          data;
    struct tree *left;
    struct tree *right;
};

static struct tree *createNewNode(int data)
{
    struct tree *newNode = malloc(sizeof(struct tree));
    newNode->data = data;
    newNode->left = NULL;
    newNode->right = NULL;
    return newNode;
}

static struct tree *insert(struct tree *root, int data)
{
    if (root == NULL)
        root = createNewNode(data);
    else if (data < root->data)
        root->left = insert(root->left, data);
    else
        root->right = insert(root->right, data);
    return root;
}

static void pr_indent(int level)
{
    for (int i = 0; i < level; i++)
        printf("    ");
}

static void inorder(struct tree *root, int level)
{
    if (root != NULL)
    {
        inorder(root->left, level + 1);
        pr_indent(level);
        printf("%d\n", root->data);
        inorder(root->right, level + 1);
    }
}

static void print_inorder(const char *tag, struct tree *root)
{
    printf("%s: \n", tag);
    inorder(root, 0);
    putchar('\n');
}

static void release(struct tree *node)
{
    if (node != NULL)
    {
        release(node->left);
        release(node->right);
        free(node);
    }
}

int main(void)
{
    struct tree *root = NULL;
    int values[] = { 37, 24, 30,36, 72, 57, 32, 62 };
    enum { NUM_VALUES = sizeof(values) / sizeof(values[0]) };

for (int i = 0; i < NUM_VALUES; i++)
    {
        root = insert(root, values[i]);
        char tag[20];
        snprintf(tag, sizeof(tag), "%d: After %d", i + 1, values[i]);
        print_inorder(tag, root);
    }

release(root);
    return 0;
}

</code>
  </pre>
  <P>
    示例输出：
  </p>
   <pre>
    <code>
      1: After 37: 
37

2: After 24: 
    24
37

3: After 30: 
    24
        30
37

4: After 36: 
    24
        30
            36
37

5: After 72: 
    24
        30
            36
37
    72

6: After 57: 
    24
        30
            36
37
        57
    72

7: After 32: 
    24
        30
                32
            36
37
        57
    72

8: After 62: 
    24
        30
                32
            36
37
        57
            62
    72

</code>
  </pre>
</DIV>