一个函数实现树的非递归前、中、后序遍历

#include<iostream>#define MAX 99using namespace std;struct BTNode {    int data;    BTNode *lchild, *rchild;};void visit(BTNode *p) {//访问    printf("%d ", p->data);}void Pre_IN_Post_order(BTNode *p,int AA) {//AA=1先序 2中序 3后序    BTNode* sta[MAX];//定义一个栈    int top = -1;//栈顶指针    int flag[MAX] = {};//记录第几次访问,初始化都是0    sta[++top] = p;    while (top!=-1) {        p = sta[top];        ++flag[top];        if (flag[top] == AA) visit(p);        switch (flag[top]) {        case 1:            if (p->lchild) sta[++top] = p->lchild; break;        case 2:            if (p->rchild) sta[++top] = p->rchild; break;        case 3:            flag[top--]=0;break;//为下一个可能入栈的元素进行初始化        }    }}int main() {    int a[5] = { 1,2,3,4,5 };    BTNode all[9];    for (int i = 0; i < 9; ++i) {        all[i].lchild = all[i].rchild = NULL;        all[i].data = i;    }    all[0].lchild = all + 1; all[0].rchild = all + 2;    all[1].lchild = all + 3; all[1].rchild = all + 4;    all[2].lchild = all + 5; all[2].rchild = all + 6;    all[4].lchild = all + 7;    all[5].rchild = all + 8;    Pre_IN_Post_order(all, 1); cout << endl;    Pre_IN_Post_order(all, 2); cout << endl;    Pre_IN_Post_order(all, 3); cout << endl;}