Binary Tree Postorder Traversal

Summary: Basic staff, need to check if goes up along the tree, that's the difference to pre-order traverse.

 1     vector<int> postorderTraversal(TreeNode *root) {
 2         vector<int> seq;
 3         if(root == NULL)
 4             return seq;
 5         stack<TreeNode *> nodes;
 6         nodes.push(root);
 7         TreeNode * pre_node = NULL;
 8         while(nodes.size() != 0) {
 9             TreeNode * node = nodes.top();
10             if(node->left == NULL && node->right == NULL || 
11                 (pre_node != NULL && (pre_node == node->left || pre_node == node->right))){
12                 pre_node = node;
13                 seq.push_back(node->val);
14                 nodes.pop();
15                 continue;
16             }
17             
18             if(node->right != NULL) {
19                 nodes.push(node->right);
20             }
21             
22             if(node->left != NULL)
23                 nodes.push(node->left);
24         }
25     }

 

posted @ 2013-11-09 15:50  假日笛声  阅读(158)  评论(0)  编辑  收藏  举报