二叉树的先中后序遍历非递归用c语言实现

好的，针对您的问题，下面是二叉树的先中后序遍历非递归算法的 C 语言实现：

先序遍历：

void preorderTraversal(struct TreeNode* root, int* returnSize) {
    int top = -1, i;
    struct TreeNode* stack[100];
    *returnSize = 0;
    if (!root) {
        return;
    }
    stack[++top] = root;
    while (top != -1) {
        root = stack[top--];
        (*returnSize)++;
        stack[++top] = root->right;
        stack[++top] = root->left;
    }
}

中序遍历：

void inorderTraversal(struct TreeNode* root, int* returnSize) {
    int top = -1, i;
    struct TreeNode* stack[100];
    *returnSize = 0;
    while (root || top != -1) {
        while (root) {
            stack[++top] = root;
            root = root->left;
        }
        if (top != -1) {
            (*returnSize)++;
            root = stack[top--];
            stack[++top] = root->right;
        }
    }
}

后序遍历：

void postorderTraversal(struct TreeNode* root, int* returnSize) {
    int top = -1, i;
    struct TreeNode* stack[100], *lastVisited = NULL;
    *returnSize = 0;
    while (root || top != -1) {
        while (root) {
            stack[++top] = root;
            root = root->left;
        }
        root = stack[top];
        if (!root->right || root->right == lastVisited) {
            (*returnSize)++;
            top--;
            lastVisited = root;
            root = NULL;
        } else {
            root = root->right;
            stack[++top] = root;
        }
    }
}

希望这些代码可以解决您的问题。