# 二叉树深度优先遍历和广度优先遍历

对于一颗二叉树，深度优先搜索(Depth First Search)是沿着树的深度遍历树的节点，尽可能深的搜索树的分支。以上面二叉树为例，深度优先搜索的顺序

下面给出二叉树dfs和bfs的具体代码：

``` 1 #include <vector>
2 #include <iostream>
3 #include <stack>
4 #include <queue>
5 using namespace std;
6
7 struct BitNode
8 {
9     int data;
10     BitNode *left, *right;
11     BitNode(int x) :data(x), left(0), right(0){}
12 };
13
14 void Create(BitNode *&root)
15 {
16     int key;
17     cin >> key;
18     if (key == -1)
19         root = NULL;
20     else
21     {
22         root = new BitNode(key);
23         Create(root->left);
24         Create(root->right);
25     }
26 }
27
28 void PreOrderTraversal(BitNode *root)
29 {
30     if (root)
31     {
32         cout << root->data << " ";
33         PreOrderTraversal(root->left);
34         PreOrderTraversal(root->right);
35     }
36 }
37
38 //深度优先搜索
39 //利用栈，现将右子树压栈再将左子树压栈
40 void DepthFirstSearch(BitNode *root)
41 {
42     stack<BitNode*> nodeStack;
43     nodeStack.push(root);
44     while (!nodeStack.empty())
45     {
46         BitNode *node = nodeStack.top();
47         cout << node->data << ' ';
48         nodeStack.pop();
49         if (node->right)
50         {
51             nodeStack.push(node->right);
52         }
53         if (node->left)
54         {
55             nodeStack.push(node->left);
56         }
57     }
58 }
59
60 //广度优先搜索
62 {
63     queue<BitNode*> nodeQueue;
64     nodeQueue.push(root);
65     while (!nodeQueue.empty())
66     {
67         BitNode *node = nodeQueue.front();
68         cout << node->data << ' ';
69         nodeQueue.pop();
70         if (node->left)
71         {
72             nodeQueue.push(node->left);
73         }
74         if (node->right)
75         {
76             nodeQueue.push(node->right);
77         }
78     }
79 }
80
81 int  main()
82 {
83     BitNode *root = NULL;
84     Create(root);
85     //前序遍历
86     PreOrderTraversal(root);
87     //深度优先遍历
88     cout << endl << "dfs" << endl;
89     DepthFirstSearch(root);
90     //广度优先搜索
91     cout << endl << "bfs" << endl;