这里我们将看到一个有趣的问题。我们有一棵二叉树。我们必须以逆时针的方式遍历树。遍历的顺序如下所示 −
遍历序列是 1, 8, 9, 10, 11, 12, 13, 14, 15, 3, 2, 4, 5, 6, 7
算法
antiClockTraverse(root)
Begin
i := 1, j := height of the tree
flag := false
while i <= j, do
if flag is false, then
print tree elements from right to left for level i
flag := true
i := i + 1
else
print tree elements from left to right for level j
flag := false
j := j - 1
end if
done
End示例
#includeusing namespace std; class Node { public: Node* left; Node* right; int data; Node(int data) { //constructor to create node this->data = data; this->left = NULL; this->right = NULL; } }; int getHeight(Node* root) { if (root == NULL) return 0; //get height of left and right subtree int hl = getHeight(root->left); int hr = getHeight(root->right); return 1 + max(hl, hr); //add 1 for root } void printLeftToRight(class Node* root, int level) { if (root == NULL) return; if (level == 1) cout << root->data << " "; else if (level > 1) { printLeftToRight(root->left, level - 1); printLeftToRight(root->right, level - 1); } } void printRightToLeft(struct Node* root, int level) { if (root == NULL) return; if (level == 1) cout << root->data << " "; else if (level > 1) { printRightToLeft(root->right, level - 1); printRightToLeft(root->left, level - 1); } } void antiClockTraverse(class Node* root) { int i = 1; int j = getHeight(root); int flag = 0; //flag is used to change direction while (i <= j) { if (flag == 0) { printRightToLeft(root, i); flag = 1; //set flag to print from left to right i++; }else { printLeftToRight(root, j); flag = 0; //set flag to print from right to left j--; } } } int main() { struct Node* root; root = new Node(1); root->left = new Node(2); root->right = new Node(3); root->left->left = new Node(4); root->left->right = new Node(5); root->right->left = new Node(6); root->right->right = new Node(7); root->left->left->left = new Node(8); root->left->left->right = new Node(9); root->left->right->left = new Node(10); root->left->right->right = new Node(11); root->right->left->left = new Node(12); root->right->left->right = new Node(13); root->right->right->left = new Node(14); root->right->right->right = new Node(15); antiClockTraverse(root); }
输出
1 8 9 10 11 12 13 14 15 3 2 4 5 6 7
