摘自計蒜客:http://www.jisuanke.com/course/35/1394
(一)、先序遍歷
先序遍歷時二叉樹遍歷的一種,對於每個結點,先訪問當前結點,然後訪問結點的左子樹,最後訪問結點的右子樹。在子樹
裏依然按照這個遍歷順序訪問。
#include<iostream>
using namespace std;
class Node {
public:
int data;
Node *lchild, *rchild;
Node(int _data) {
data = _data;
lchild = NULL;
rchild = NULL;
}
~Node() {
if (lchild != NULL) {
delete lchild;
}
if (rchild != NULL) {
delete rchild;
}
}
void preorder(){
cout << data << " ";
if (lchild != NULL) {
lchild->preorder();
}
if (rchild != NULL) {
rchild->preorder();
}
}
};
class BinaryTree {
private:
Node *root;
public:
BinaryTree() {
root = NULL;
}
~BinaryTree() {
if (root != NULL) {
delete root;
}
}
void build_demo() {
root = new Node(1);
root->lchild = new Node(2);
root->rchild = new Node(3);
root->lchild->lchild = new Node(4);
root->lchild->rchild = new Node(5);
root->rchild->rchild = new Node(6);
}
void preorder() {
root->preorder();
}
};
int main() {
BinaryTree binarytree;
binarytree.build_demo();
binarytree.preorder();
cout << endl;
return 0;
}
(二)、中序遍歷
中序遍歷和先序遍歷類似,只是在遍歷順序上有所不同,中序遍歷先訪問當前結點的左子樹,然後訪問當前結點,最後訪問
子樹。如果左右孩子不爲空,則遞歸調用孩子結點的中序遍歷函數。
#include<iostream>
using namespace std;
class Node {
...
public:
void inorder() {
if (lchild != NULL) {
lchild->inorder();
}
cout << data << " ";
if (rchild != NULL) {
rchild->inorder();
}
}
};
class BinaryTree {
...
public:
void inorder() {
root->inorder();
}
};
(三)、後序遍歷
後序遍歷先訪問當前結點的左子樹,然後訪問當前結點的右子樹,最後訪問當前結點。如果當前結點的左右子樹不爲空,則
遞歸調用左右孩子的後序遍歷函數。
#include<iostream>
using namespace std;
class Node {
...
public:
void postorder() {
if (lchild != NULL) {
lchild->postorder();
}
if (rchild != NULL) {
rchild->postorder();
}
cout << data << " ";
}
};
class BinaryTree {
...
public:
void postorder() {
root->postorder();
}
};