leetcode 145 Binary Tree Postorder Traversal C++

后续遍历。

vector<int> postorderTraversal(TreeNode* root) {
stack<TreeNode*> stack;
vector<int> result;
if(!root) return result;
stack.push(root);
while(!stack.empty()) {
TreeNode *node = stack.top();
if(!node->left&&!node->right) {
result.push_back(node->val);
stack.pop();
}
if(node->right) {
stack.push(node->right);
node->right = NULL;
}
if(node->left) {
stack.push(node->left);
node->left = NULL;
}
}
return result;
}