标签：des style blog http os io strong for
详见：剑指 Offer 题目汇总索引：第6题
Given a binary tree, return the postorder traversal of its nodes‘ values.
For example: Given binary tree {1,#,2,3},
1
2
/
3
return [3,2,1].
Note: Recursive solution is trivial, could you do it iteratively?
注：后序遍历是较麻烦的一个，不可大意。关键两点： 1.要走到 p->left | p->right ==0, 2.每次出栈出两个结点。
/**
* 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<int> postorderTraversal(TreeNode *root) {
vector<int> answer;
if(root == NULL) return answer;
stack<TreeNode*> st;
st.push(root);
TreeNode *p = root;
while(p->right || p->left) {
while(p->left) { st.push(p->left); p = p->left;}
if(p->right) { st.push(p->right); p = p->right;}
}
while(!st.empty()) {
TreeNode *q = st.top(); st.pop();
answer.push_back(q->val);
if(!st.empty()) {
TreeNode *q2 = st.top();
while(q2->right && q2->right != q) {
st.push(q2->right); q2 = q2->right;
while(q2->left || q2->right) {
while(q2->left){ st.push(q2->left); q2 = q2->left;}
if(q2->right){ st.push(q2->right); q2 = q2->right;}
}
}
}
}
return answer;
}
};
Given a binary tree, return the preorder traversal of its nodes‘ values.
For example: Given binary tree {1,#,2,3},
1
2
/
3
return [1,2,3].
Note: Recursive solution is trivial, could you do it iteratively?
/**
* 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<int> preorderTraversal(TreeNode *root) {
vector<int> vec;
if(root == NULL) return vec;
stack<TreeNode*> st;
st.push(root);
while(!st.empty()) {
TreeNode *p = st.top(); st.pop();
vec.push_back(p->val);
if(p->right) st.push(p->right);
if(p->left) st.push(p->left);
}
return vec;
}
};
Binary Tree Postorder Traversal && Binary Tree Preorder Traversal,布布扣,bubuko.com
Binary Tree Postorder Traversal && Binary Tree Preorder Traversal
标签：des style blog http os io strong for
原文地址：http://www.cnblogs.com/liyangguang1988/p/3902276.html
