标签：des blog for io div leetcode
树的层次遍历，比较简单，3个题的做法完全一样，只是在特定的地方对结果进行reverse。
1、Binary Tree Level Order Traversal
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<vector<int> > levelOrder(TreeNode *root) {
vector<vector<int> > result;
vector<TreeNode *> levelNodes;
if (root == NULL) {
return result;
}
levelNodes.push_back(root);
while (levelNodes.size() > 0) {
vector<TreeNode *> nextLevelNodes;
vector<int> levelVals;
for (int i = 0; i < levelNodes.size(); i++) {
levelVals.push_back(levelNodes[i]->val);
if (levelNodes[i]->left != NULL) {
nextLevelNodes.push_back(levelNodes[i]->left);
}
if (levelNodes[i]->right != NULL) {
nextLevelNodes.push_back(levelNodes[i]->right);
}
}
result.push_back(levelVals);
levelNodes = nextLevelNodes;
}
return result;
}
};
2、 Binary Tree Level Order Traversal II
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<vector<int> > levelOrderBottom(TreeNode *root) {
vector<vector<int> > result;
vector<TreeNode *> levelNodes;
if (root != NULL) {
levelNodes.push_back(root);
}
while (levelNodes.size() > 0) {
vector<TreeNode *> next;
vector<int> nodeValues;
for (int i = 0; i < levelNodes.size(); i++) {
nodeValues.push_back(levelNodes[i]->val);
if (levelNodes[i]->left != NULL) {
next.push_back(levelNodes[i]->left);
}
if (levelNodes[i]->right != NULL) {
next.push_back(levelNodes[i]->right);
}
}
result.push_back(nodeValues);
levelNodes = next;
}
reverse(result.begin(), result.end());
return result;
}
};
3、Binary Tree Zigzag Level Order Traversal
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<vector<int> > zigzagLevelOrder(TreeNode *root) {
vector<vector<int> > result;
vector<TreeNode *> nodes;
if (root != NULL) {
nodes.push_back(root);
}
bool flag = false;
while (nodes.size() > 0) {
vector<TreeNode *> next;
vector<int> values;
for (int i = 0; i < nodes.size(); i++) {
values.push_back(nodes[i]->val);
if (nodes[i]->left != NULL) {
next.push_back(nodes[i]->left);
}
if (nodes[i]->right != NULL) {
next.push_back(nodes[i]->right);
}
}
if (flag) {
reverse(values.begin(), values.end());
}
result.push_back(values);
nodes = next;
flag = !flag;
}
return result;
}
};
[Leetcode][Tree][Binary Tree Level Order Traversal ],布布扣,bubuko.com
[Leetcode][Tree][Binary Tree Level Order Traversal ]
标签：des blog for io div leetcode
原文地址：http://www.cnblogs.com/poemqiong/p/3815013.html
