二叉树的构建和遍历

  1 #include <iostream>
  2 using namespace std;
  3 const int N = 9;
  4 int order[1 << N], k = 0;
  5 struct TreeNode {
  6 	int val;
  7 	TreeNode *leftChild;
  8 	TreeNode *rightChild;
  9 	TreeNode() : TreeNode(0) {}
 10 	TreeNode(int x) : val(x), leftChild(nullptr), rightChild(nullptr) {}
 11 };
 12 int number;
 13 void createBinaryTree(TreeNode *&root)
 14 {
 15 
 16 	cin >> number;
 17 	if (number == -1)
 18 		return;
 19 	root = new TreeNode(number);
 20 	createBinaryTree(root->leftChild);
 21 	createBinaryTree(root->rightChild);
 22 }
 23 
 24 void preOrderTraverse(TreeNode *root, int order[], int *k) {
 25 	if (root == nullptr)
 26 		return;
 27 	order[(*k)++] = root->val;
 28 	preOrderTraverse(root->leftChild, order, k);
 29 	preOrderTraverse(root->rightChild, order, k);
 30 }
 31 
 32 void inOrderTraverse(TreeNode *root, int order[], int *k)
 33 {
 34 	if (root == nullptr)return;
 35 	inOrderTraverse(root->leftChild, order, k);
 36 	order[(*k)++] = root->val;
 37 	inOrderTraverse(root->rightChild, order, k);
 38 }
 39 
 40 void postOrderTraverse(TreeNode *root, int order[], int *k)
 41 {
 42 	if (root == nullptr)return;
 43 	postOrderTraverse(root->leftChild, order, k);
 44 
 45 	postOrderTraverse(root->rightChild, order, k);
 46 	order[(*k)++] = root->val;
 47 }
 48 void print()
 49 {
 50 	for (int i = 0; i < k; i++)
 51 	{
 52 		if (i == 0)
 53 			cout << order[i];
 54 		else
 55 			cout << " " << order[i];
 56 	}
 57 	cout << endl;
 58 }
 59 int main()
 60 {
 61 	TreeNode *root = nullptr;
 62 	createBinaryTree(root);
 63 
 64 
 65 
 66 	preOrderTraverse(root, order, &k);
 67 
 68 	print();
 69 	k = 0;
 70 	inOrderTraverse(root, order, &k);
 71 
 72 	print();
 73 	k = 0;
 74 	postOrderTraverse(root, order, &k);
 75 
 76 	print();
 77 	return 0;
 78 }
 79