二叉树遍历 非递归算法

#include <cstdio>
#include <cstring>

int all, top;
class TreeNode{
    public:
        int value;
        TreeNode* left;
        TreeNode* right;
        TreeNode(int _value, TreeNode *_left, TreeNode *_right)
        {
            value = _value;
            left = _left;
            right = _right;
        }
};
TreeNode *stack[105];
int result[105];

void preorderTraversal(TreeNode *root, int *result)// 前序遍历
{
    top = all = 0;
    if(root != NULL)
        stack[top++] = root;// 根节点入栈
    while(top > 0)
    {
        TreeNode* now = stack[--top];
        result[all++] = now->value;
        if(now -> right != NULL)
            stack[top++] = now->right;// 插入右节点
        if(now -> left != NULL)
            stack[top++] = now->left;// 插入左节点
    }
}

void inorderTraversal(TreeNode *root, int *result)// 中序遍历
{
    top = all = 0;
    TreeNode* now = root;
    while(1)
    {
        while(now != NULL)// 先到最左边的儿子 
        {
            stack[top++] = now;// 父节点入栈
            now = now->left;
        }
        if(top == 0) break;
        now = stack[--top];// 若无右儿子取父亲
        result[all++] = now->value;
        now = now->right;// 先右儿子
    }
}

void postorderTraversal(TreeNode *root, int *result)// 后序遍历
{
    top = all = 0;
    TreeNode* now = root;
    while(1)
    {
        while(now->left != NULL || now->right != NULL)// 找出下一个节点
        {
            stack[top++] = now; // 当前节点入栈
            if(now->left != NULL)
            {
                now = now->left;
                stack[top-1]->left = NULL;// 删除父亲节点的左儿子
            }
            else
            {
                now = now->right;
                stack[top-1]->right = NULL;// 删除父亲节点的右儿子
            }
        }
        result[all++] = now->value;
        if(top == 0) break;
        now = stack[--top];
    }
}

int main()
{
/*
        0
        /        1 5
       /\         2 3  6
        /
        4
*/
/*    
    TreeNode* t6 = new TreeNode(6, NULL, NULL);
    TreeNode* t5 = new TreeNode(5, NULL, t6);
    TreeNode* t4 = new TreeNode(4, NULL, NULL);
    TreeNode* t3 = new TreeNode(3, t4, NULL);
    TreeNode* t2 = new TreeNode(2, NULL, NULL);
    TreeNode* t1 = new TreeNode(1, t2, t3);
    TreeNode* t0 = new TreeNode(0, t1, t5);

    preorderTraversal(t0, result);
    for(int i = 0; i < all; i++)
        printf("%d ", result[i]);
    printf("\n");

    inorderTraversal(t0, result);
    for(int i = 0; i < all; i++)
        printf("%d ", result[i]);
    printf("\n");

    postorderTraversal(t0, result);
    for(int i = 0; i < all; i++)
        printf("%d ", result[i]);
    printf("\n");
*/
    return 0;
}