2

Author: kedebug

BinaryTreePostorderTraversal/BinaryTreePostorderTraversal.cc

@@ -0,0 +1,51 @@
+/**
+ * Definition for binary tree
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    void print(vector<int>& result, TreeNode* from, TreeNode* to) {
+        vector<int> temp;
+        while (true) {
+            temp.push_back(from->val);
+            if (from == to) {
+                break;
+            }
+            from = from->right;
+        }
+        for (int i = temp.size() - 1; i >= 0; i--) {
+            result.push_back(temp[i]);
+        }
+    }
+    
+    vector<int> postorderTraversal(TreeNode *root) {
+        vector<int> result;
+        TreeNode prev(0);
+        prev.left = root;
+        TreeNode* curr = &prev;
+        while (curr != NULL) {
+            if (curr->left == NULL) {
+                curr = curr->right;
+            } else {
+                TreeNode* next = curr->left;
+                while (next->right && next->right != curr) {
+                    next = next->right;
+                }
+                if (next->right == NULL) {
+                    next->right = curr;
+                    curr = curr->left;
+                } else {
+                    print(result, curr->left, next);
+                    next->right = NULL;
+                    curr = curr->right;
+                }
+            }
+        }
+        return result;
+    }
+};