利用先序序列非递归程序建立二叉树，并输出先序、中序和后序序列,使用c语言

以下是利用先序序列非递归程序建立二叉树，并输出先序、中序和后序序列的C语言代码：

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

// 定义二叉树结构体
typedef struct TreeNode {
    char data;
    struct TreeNode *left;
    struct TreeNode *right;
} TreeNode;

// 定义栈结构体
typedef struct StackNode {
    TreeNode *node;
    struct StackNode *next;
} StackNode;

// 初始化栈
void initStack(StackNode **stack) {
    *stack = NULL;
}

// 判断栈是否为空
int isStackEmpty(StackNode *stack) {
    return stack == NULL ? 1 : 0;
}

// 入栈
void push(StackNode **stack, TreeNode *node) {
    StackNode *newNode = (StackNode*)malloc(sizeof(StackNode));
    newNode->node = node;
    newNode->next = *stack;
    *stack = newNode;
}

// 出栈
TreeNode* pop(StackNode **stack) {
    if (isStackEmpty(*stack)) {
        return NULL;
    }
    TreeNode *node = (*stack)->node;
    StackNode *temp = *stack;
    *stack = (*stack)->next;
    free(temp);
    return node;
}

// 先序遍历二叉树
void preOrder(TreeNode *root) {
    if (root == NULL) {
        return;
    }
    printf("%c ", root->data);
    preOrder(root->left);
    preOrder(root->right);
}

// 中序遍历二叉树
void inOrder(TreeNode *root) {
    if (root == NULL) {
        return;
    }
    inOrder(root->left);
    printf("%c ", root->data);
    inOrder(root->right);
}

// 后序遍历二叉树
void postOrder(TreeNode *root) {
    if (root == NULL) {
        return;
    }
    postOrder(root->left);
    postOrder(root->right);
    printf("%c ", root->data);
}

// 建立二叉树
TreeNode* createBinaryTree(char preOrder[], int size) {
    StackNode *stack;
    initStack(&stack);

    TreeNode *root = (TreeNode*)malloc(sizeof(TreeNode));
    root->data = preOrder[0];
    root->left = NULL;
    root->right = NULL;
    push(&stack, root);

    int i = 1;
    while (i < size) {
        TreeNode *current = (TreeNode*)malloc(sizeof(TreeNode));
        current->data = preOrder[i];
        current->left = NULL;
        current->right = NULL;

        if (preOrder[i] == '#') {
            TreeNode *parent = pop(&stack);
            while (!isStackEmpty(stack) && parent->right != NULL) {
                parent = pop(&stack);
            }
            if (parent->right == NULL) {
                parent->right = current;
            } else {
                printf("Invalid input!\n");
                return root;
            }
        } else {
            TreeNode *parent = peek(stack);
            if (parent == NULL) {
                printf("Invalid input!\n");
                return root;
            }
            if (parent->left == NULL) {
                parent->left = current;
            } else {
                parent = pop(&stack);
                while (!isStackEmpty(stack) && parent->right != NULL) {
                    parent = pop(&stack);
                }
                if (parent->right == NULL) {
                    parent->right = current;
                } else {
                    printf("Invalid input!\n");
                    return root;
                }
            }
            push(&stack, current);
        }
        i++;
    }
    return root;
}

// 获取栈顶元素
TreeNode* peek(StackNode *stack) {
    if (isStackEmpty(stack)) {
        return NULL;
    }
    return stack->node;
}

int main() {
    char preOrder[] = {'A', 'B', 'D', '#', '#', 'E', '#', '#', 'C', 'F', '#', '#', 'G', '#', '#'};
    int size = sizeof(preOrder) / sizeof(preOrder[0]);

    TreeNode *root = createBinaryTree(preOrder, size);
    printf("PreOrder: ");
    preOrder(root);
    printf("\n");
    printf("InOrder: ");
    inOrder(root);
    printf("\n");
    printf("PostOrder: ");
    postOrder(root);
    printf("\n");

    return 0;
}

输入先序序列（例如：ABD##E##CF##G##），程序会依次建立二叉树并输出先序、中序和后序序列。