add prob #I17.12; iterative solution

Author: randomwalk10

I17_12_BiNode_LCCI.cpp

@@ -0,0 +1,78 @@
+/*
+The data structure TreeNode is used for binary tree, but it can also used to represent a single linked list (where left is null, and right is the next node in the list). Implement a method to convert a binary search tree (implemented with TreeNode) into a single linked list. The values should be kept in order and the operation should be performed in place (that is, on the original data structure).
+
+Return the head node of the linked list after converting.
+
+Note: This problem is slightly different from the original one in the book.
+
+ 
+
+Example:
+
+Input:  [4,2,5,1,3,null,6,0]
+Output:  [0,null,1,null,2,null,3,null,4,null,5,null,6]
+Note:
+
+The number of nodes will not exceed 100000.
+
+来源：力扣（LeetCode）
+链接：https://leetcode-cn.com/problems/binode-lcci
+著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
+*/
+
+#include <stack>
+using namespace std;
+
+struct TreeNode {
+    int val;
+    TreeNode *left;
+    TreeNode *right;
+    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+};
+
+class Solution {
+public:
+    TreeNode* convertBiNode(TreeNode* root) {
+		TreeNode* res = NULL;
+		if(NULL==root) return res;
+
+		stack<TreeNode*> s_parent;
+		stack<bool> s_visited;
+		TreeNode* tail = NULL;
+
+		s_parent.push(root);
+		s_visited.push(false);
+		while(!s_parent.empty()){
+			TreeNode* tmp_node = s_parent.top(); s_parent.pop();
+			bool tmp_visited = s_visited.top(); s_visited.pop();
+			if(tmp_visited){
+				if(res==NULL){
+					res = tmp_node; // head
+					tail = tmp_node;
+				}
+				else{
+					tail->right = tmp_node;
+					tail = tmp_node;
+				}
+				tail->left = NULL;
+			}
+			else{
+				//right
+				if(tmp_node->right){
+					s_parent.push(tmp_node->right);
+					s_visited.push(false);
+				}
+				//self
+				s_parent.push(tmp_node);
+				s_visited.push(true);
+				//left
+				if(tmp_node->left){
+					s_parent.push(tmp_node->left);
+					s_visited.push(false);
+				}
+			}
+		}
+		
+		return res;
+    }
+};