int main() { TreeNode *root, *p, *pp; Initiate(&root); p = InsertLeftNode(root, 'A'); p = InsertLeftNode(p, 'B'); pp=p; p = InsertLeftNode(p, 'D'); p = InsertRightNode(pp, 'E'); p = InsertLeftNode(p, 'H'); p = InsertRightNode(root->leftChild, 'C'); pp = p; InsertLeftNode(p, 'F'); p = InsertRightNode(p, 'I'); InsertRightNode(pp, 'G'); PrintBiTree(root->leftChild, 1); return 0; }改变代码让I成为F的左子树

可以将原来的代码中的以下几行修改：

pp = p;
p = InsertRightNode(p, 'I');
InsertRightNode(pp, 'G');

改为：

pp = p->leftChild;
p->leftChild = InsertRightNode(p->leftChild, 'I');
InsertRightNode(pp, 'G');

这样就可以将I成为F的左子树了。完整代码如下：

#include <stdio.h>
#include <stdlib.h>

typedef struct TreeNode {
    char data;
    struct TreeNode *leftChild;
    struct TreeNode *rightChild;
} TreeNode;

void Initiate(TreeNode **root) {
    *root = (TreeNode*)malloc(sizeof(TreeNode));
    (*root)->data = '\0';
    (*root)->leftChild = NULL;
    (*root)->rightChild = NULL;
}

TreeNode* InsertLeftNode(TreeNode *p, char x) {
    TreeNode *newNode = (TreeNode*)malloc(sizeof(TreeNode));
    newNode->data = x;
    newNode->leftChild = NULL;
    newNode->rightChild = NULL;
    p->leftChild = newNode;
    return newNode;
}

TreeNode* InsertRightNode(TreeNode *p, char x) {
    TreeNode *newNode = (TreeNode*)malloc(sizeof(TreeNode));
    newNode->data = x;
    newNode->leftChild = NULL;
    newNode->rightChild = NULL;
    p->rightChild = newNode;
    return newNode;
}

void PrintBiTree(TreeNode *p, int depth) {
    if (p != NULL) {
        PrintBiTree(p->rightChild, depth+1);
        for (int i = 0; i < depth-1; i++) {
            printf("    ");
        }
        if (depth > 0) {
            printf("---");
        }
        printf("%c\n", p->data);
        PrintBiTree(p->leftChild, depth+1);
    }
}

int main() {
    TreeNode *root, *p, *pp;
    Initiate(&root);
    p = InsertLeftNode(root, 'A');
    p = InsertLeftNode(p, 'B');
    pp = p->leftChild;
    p = InsertLeftNode(p, 'D');
    p = InsertRightNode(pp, 'E');
    p = InsertLeftNode(p, 'H');
    p =RightNode(root->leftChild, 'C');
    pp = p->leftChild;
    p->leftChild = InsertRightNode(p->leftChild, 'F');
    p = InsertRightNode(p, 'I');
    InsertRightNode(pp, 'G');
    PrintBiTree(root->leftChild, 1);
    return 0;
}