10-二叉树-非递归遍历

二叉树的非递归遍历

#include<stdio.h>
#include<stdlib.h>
#include"myStack.h"  //使用数组形式的栈
//非递归遍历可以使用下列规则
/*
每个节点设置一个标志位，默认状态为假

- 将根节点压入栈中
- 进入循环：只要栈中元素个数大于0，进行循环操作
  - 弹出栈顶元素
  - 如果这个栈顶元素标志为真，输出这个元素并执行下一次循环
  - 如果栈顶元素标志为假，将节点的标志设为真
  - 将该节点的右子树、左子树、根压入到栈中
  - 执行下一次循环
*/

#define FALSE 0
#define TRUE  1
struct myBinaryTree{
    char ch;  //数据域
    struct myBinaryTree* lChild;
    struct myBinaryTree* rChild;
    int flag;
};

//参数：根节点
void foreachPrint(struct myBinaryTree* b){
    if(NULL == b){
        return;
    }

    myStackType* st = init_stack();  //初始化一个栈

    push_stack(st, b); //根节点入栈

    while(size_stack(st) > 0){  //栈中元素大于0，继续循环
        //获取栈顶元素，并出栈
        struct myBinaryTree* curNode = top_stack(st);
        pop_stack(st);

        if(curNode->flag == TRUE){  //标志位为真
            printf("%c\n", curNode->ch);
            continue;
        }else{    //标志位为假
            curNode->flag = TRUE;

            if(curNode->rChild != NULL){    //子树为空就不入栈
                push_stack(st, curNode->rChild);  
            }
            if(curNode->lChild != NULL){
                push_stack(st, curNode->lChild);
            }
            
            push_stack(st, curNode);
        }
    }
}

int main(){

    struct myBinaryTree bt1 = {'A',NULL,NULL, FALSE};
    struct myBinaryTree bt2 = {'B',NULL,NULL, FALSE};
    struct myBinaryTree bt3 = {'C',NULL,NULL, FALSE};
    struct myBinaryTree bt4 = {'D',NULL,NULL, FALSE};
    struct myBinaryTree bt5 = {'E',NULL,NULL, FALSE};
    struct myBinaryTree bt6 = {'F',NULL,NULL, FALSE};
    struct myBinaryTree bt7 = {'G',NULL,NULL, FALSE};
    struct myBinaryTree bt8 = {'H',NULL,NULL, FALSE};

    bt1.lChild = &bt2;
    bt1.rChild = &bt6;

    bt2.rChild = &bt3;

    bt3.lChild = &bt4;
    bt3.rChild = &bt5;

    bt6.rChild = &bt7;
    bt7.lChild = &bt8;

    foreachPrint(&bt1);
    return 0;
}