二叉树的建立和基础操作<三> —— (三种遍历及分层打印)

#include<iostream>
#include<vector>
#include<queue>
#include<math.h>
#include<string.h>
#include<algorithm>
using namespace std;
typedef struct BinaryTree
{
char val;
struct  BinaryTree *left;
struct  BinaryTree *right;
}BinaryTree,*BitTree;

//******递归建立二叉树*****//
//先建立根节点，再建立左子树，最后建立右子树
/***********
测试用例:
a
b         c
#    d    #    e
f   #     #   #
#   #
输入:ab#df###c#e##
***************/
int create_tree(BitTree &T)
{
char val = getchar();
if(val == '#')
T = NULL;
else
{
T = new BinaryTree;
T -> val = val;
create_tree(T->left);
create_tree(T->right);
}
return 0;
}

//*****前序递归遍历二叉树*****//
void Preorder(BitTree T)
{
if(T)
{
cout<<T->val<<" ";
Preorder(T->left);
Preorder(T->right);
}
}

//*****中序递归遍历二叉树*****//
void Midorder(BitTree T)
{
if(T)
{
Midorder(T->left);
cout<<T->val<<" ";
Midorder(T->right);
}
}

//*****后序递归遍历二叉树*****//
void behindorder(BitTree T)
{
if(T)
{
behindorder(T->left);
behindorder(T->right);
cout<<T->val<<" ";
}
}

//*****按层遍历*****//

//设置游标last，分层打印二叉树
int layerorder_1(BitTree T)
{
vector<BitTree> vec;
vec.push_back(T);
int cur = 0;
int last = 1;
while(cur < vec.size())
{
last = vec.size();//设置last游标
while(cur < last) //当last == cur时，退出循环，打印回车
{
cout<<vec[cur]->val<<" ";
if(vec[cur]->left)
vec.push_back(vec[cur]->left);
if(vec[cur]->right)
vec.push_back(vec[cur]->right);
cur++;
}
cout<<endl;
}
return 0;
}
//改写BFS，分层打印二叉树
int layerorder_2(BitTree T)
{
int parentSize = 1, childSize = 0;
BitTree temp;
queue<BitTree > q;
q.push(T);
do{
temp = q.front();
cout<<temp->val<<" ";
q.pop();
parentSize--; //每次pop一个节点，parentSize减去1
if(temp->left)
{
q.push(temp->left);
childSize++;
}
if(temp->right)
{
q.push(temp->right);
childSize++;
}

if(parentSize == 0) //当根节点出栈完毕时，表示本层可以输出回车了
{                    //此时更新下一层parentSize,将childSize写入
parentSize = childSize; //childSize 赋值为0
childSize = 0;
cout<<endl;
}

}while(!q.empty());
return 0;

}
int main()
{
BitTree T;
create_tree(T);
cout<<"前序遍历结果（递归）:"<<endl;
Preorder(T);
cout<<endl<<"中序遍历结果（递归）:"<<endl;
Midorder(T);
cout<<endl<<"后序遍历结果（递归）:"<<endl;
behindorder(T);
cout<<endl<<"层次遍历结果1："<<endl;
layerorder_1(T);
cout<<endl<<"层次遍历结果2："<<endl;
layerorder_2(T);
return 0;

}