打印二叉树某一层次的值(重点)

方法一：递归

 1 void printNLevel(TreeNode *root, int n)
 2 {
 3     if (root == NULL)
 4     {
 5         return ;
 6     }
 7
 8     if (n == 1)
 9     {
10         cout << root->data << endl;
11     }
12     else
13     {
14         printNLevel(root->left, n-1);
15         printNLevel(root->right, n-1);
16     }
17 }  

方法二：层次遍历

 1 void TransLevel2(Node* root,int level)
 2 {
 3     if(root == NULL)
 4         return ;
 5     else
 6     {
 7         int count_levels,count_nodes,level_nodes;
 8         Node* tmp;
 9         Queue<Node*> queue;
10         queue.EnQueue(root);
11
12         count_levels=1;
13
14         while(!queue.IsEmpty())
15         {
16             if(count_levels == level)
17                 break;
18
19             count_nodes = 0;
20
21             level_nodes = queue.Size();
22
23             while(count_nodes < level_nodes)
24             {
25                tmp = queue.DeQueue();
26
27                if(tmp->left != NULL)
28                     queue.EnQueue(tmp->left);
29
30                if(tmp->right != NULL)
31                     queue.EnQueue(tmp->right);
32
33                count_nodes++;
34             }
35
36             count_levels++;
37         }
38
39         PrintQueue(queue);
40     }
41 }