题目描述
请实现一个函数按照之字形打印二叉树,即第一行按照从左到右的顺序打印,第二层按照从右至左的顺序打印,第三行按照从左到右的顺序打印,其他行以此类推。
/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};
*/
class Solution {
public:
vector<vector<int> > Print(TreeNode* pRoot) {
stack<TreeNode*> oneLevel;
vector<vector<int> > res;
if(pRoot==NULL) {
return res;
}
oneLevel.push(pRoot);
while(!oneLevel.empty()) {
vector<int> thisLevelElement;
stack<TreeNode*> nextLevel;
while (!oneLevel.empty())
{
TreeNode* temp=oneLevel.top();
thisLevelElement.push_back(temp->val);
if(res.size()%2==0) {
if(temp->left!=NULL) {
nextLevel.push(temp->left);
}
if(temp->right!=NULL) {
nextLevel.push(temp->right);
}
} else {
if(temp->right!=NULL) {
nextLevel.push(temp->right);
}
if(temp->left!=NULL) {
nextLevel.push(temp->left);
}
}
oneLevel.pop();
}
res.push_back(thisLevelElement);
oneLevel=nextLevel;
}
return res;
}
};
题目描述
从上到下按层打印二叉树,同一层结点从左至右输出。每一层输出一行。
class Solution {
public:
vector<vector<int> > Print(TreeNode* pRoot) {
queue<TreeNode*> oneLevel;
vector<vector<int> > res;
if(pRoot==NULL) {
return res;
}
oneLevel.push(pRoot);
while(!oneLevel.empty()) {
vector<int> thisLevelElement;
queue<TreeNode*> nextLevel;
while (!oneLevel.empty())
{
TreeNode* temp=oneLevel.front();
thisLevelElement.push_back(temp->val);
if(temp->left!=NULL) {
nextLevel.push(temp->left);
}
if(temp->right!=NULL) {
nextLevel.push(temp->right);
}
oneLevel.pop();
}
res.push_back(thisLevelElement);
oneLevel=nextLevel;
}
return res;
}
};