二叉树的三种非递归遍历方式

 1 void PreorderTraversal(BinTree BT)
 2 {
 3     BinTree T;
 4     std::stack<BinTree> BtStack;
 5     T = BT;
 6     while (T || !BtStack.empty())
 7     {
 8         while (T)
 9         {
10             BtStack.push(T);
11             printf("%c ", T->Data);
12             T = T->Left;
13         }
14         T = BtStack.top();
15         BtStack.pop();
16         T = T->Right;
17 
18     }
19 }

 1 void InorderTraversal(BinTree BT)
 2 {
 3     BinTree T;
 4     std::stack<BinTree> BtStack;
 5     T = BT;
 6     while (T || !BtStack.empty())
 7     {
 8         while (T)
 9         {
10             BtStack.push(T);
11             T = T->Left;
12         }
13         T = BtStack.top();
14         BtStack.pop();
15         printf("%c ", T->Data);
16         T = T->Right;
17 
18     }
19 }

1 typedef Position BinTree;    //二叉树类型
2 struct TNode {
3     ElementType Data;    //结点数据
4     int visit;
5     BinTree Left;        //指向左子树
6     BinTree Right;        //指向右子树
7 };

 1 void PostorderTraversal(BinTree BT)
 2 {
 3     BinTree T = BT;
 4     std::stack<BinTree> BtStack;
 5     while (T || !BtStack.empty())
 6     {
 7         while (T)
 8         {
 9             T->visit++;
10             BtStack.push(T);
11             T = T->Left;
12         }
13         if (!BtStack.empty())
14         {
15             T = BtStack.top();        //第二次或第三次访问该结点
16         
17             if (T->visit == 2)                //当visit == 2时，该结点已经被访问了3次，所以可以被输出了
18             {
19                 printf("%c ", T->Data);
20                 BtStack.pop();
21                 T = NULL;
22             }
23             else
24             {
25                 T->visit++;        //第二次访问
26                 T = T->Right;    //即将进入第三次访问
27             }
28         }
29     }
30 }