二叉树中序遍历非递归c语言

以下是C语言实现二叉树中序遍历的非递归算法：

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

struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
};

struct Stack {
    struct TreeNode **data;
    int top;
    int size;
};

void initStack(struct Stack *s, int size) {
    s->data = (struct TreeNode **)malloc(sizeof(struct TreeNode *) * size);
    s->top = -1;
    s->size = size;
}

void push(struct Stack *s, struct TreeNode *node) {
    if (s->top == s->size - 1) {
        return;
    }
    s->top++;
    s->data[s->top] = node;
}

struct TreeNode *pop(struct Stack *s) {
    if (s->top == -1) {
        return NULL;
    }
    struct TreeNode *node = s->data[s->top];
    s->top--;
    return node;
}

int isEmpty(struct Stack *s) {
    return s->top == -1;
}

void inorderTraversal(struct TreeNode *root) {
    if (root == NULL) {
        return;
    }
    struct Stack s;
    initStack(&s, 100);
    struct TreeNode *p = root;
    while (p != NULL || !isEmpty(&s)) {
        while (p != NULL) {
            push(&s, p);
            p = p->left;
        }
        if (!isEmpty(&s)) {
            p = pop(&s);
            printf("%d ", p->val);
            p = p->right;
        }
    }
}

int main() {
    struct TreeNode *root = (struct TreeNode *)malloc(sizeof(struct TreeNode));
    root->val = 1;
    root->left = (struct TreeNode *)malloc(sizeof(struct TreeNode));
    root->left->val = 2;
    root->left->left = NULL;
    root->left->right = NULL;
    root->right = (struct TreeNode *)malloc(sizeof(struct TreeNode));    root->right->val = 3;
    root->right->left = (struct TreeNode *)malloc(sizeof(struct TreeNode));
    root->right->left->val = 4;
    root->right->left->left = NULL;
    root->right->left->right = NULL;
    root->right->right = (struct TreeNode *)malloc(sizeof(struct TreeNode));
    root->right->right->val = 5;
    root->right->right->left = NULL;
    root->right->right->right = NULL;
    inorderTraversal(root); // 输出：2 1 4 3 5
    return 0;
}