Java实现二叉树的遍历
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public
class
BinaryTreeNode {
int
value;
BinaryTreeNode left;
BinaryTreeNode right;
// 前序遍历
public
static
void
preOrder(BinaryTreeNode tree) {
if
(tree ==
null
)
return
;
System.out.print(tree.value +
" "
);
preOrder(tree.left);
preOrder(tree.right);
}
/**
* 二叉树前序遍历的循环实现方式
*
* @param tree
*/
public
static
void
preOrderLoop(BinaryTreeNode tree) {
if
(tree ==
null
)
return
;
Stack<BinaryTreeNode> stack =
new
Stack<BinaryTreeNode>();
BinaryTreeNode node = tree;
while
(node !=
null
|| !stack.isEmpty()) {
if
(node !=
null
) {
stack.push(node);
System.out.print(node.value +
" "
);
node = node.left;
}
else
{
BinaryTreeNode item = stack.pop();
node = item.right;
}
}
}
// 中序遍历
public
static
void
inOrder(BinaryTreeNode tree) {
if
(tree ==
null
)
return
;
inOrder(tree.left);
System.out.print(tree.value +
" "
);
inOrder(tree.right);
}
/**
* 二叉树中序遍历的循环实现
*
* @param tree
*/
public
static
void
inOrderLoop(BinaryTreeNode tree) {
if
(tree ==
null
)
return
;
Stack<BinaryTreeNode> stack =
new
Stack<BinaryTreeNode>();
BinaryTreeNode node = tree;
while
(node !=
null
|| !stack.empty()) {
if
(node !=
null
) {
stack.push(node);
node = node.left;
}
else
{
BinaryTreeNode item = stack.pop();
System.out.print(item.value +
" "
);
node = item.right;
}
}
}
// 后序遍历
public
static
void
postOrder(BinaryTreeNode tree) {
if
(tree ==
null
)
return
;
postOrder(tree.left);
postOrder(tree.right);
System.out.print(tree.value +
" "
);
}
/**
* 二叉树后序遍历的循环实现
*
* @param tree
*/
public
static
void
postOrderLoop(BinaryTreeNode tree) {
if
(tree ==
null
)
return
;
HashSet<BinaryTreeNode> visited =
new
HashSet<BinaryTreeNode>();
Stack<BinaryTreeNode> stack =
new
Stack<BinaryTreeNode>();
BinaryTreeNode node = tree;
while
(node !=
null
|| !stack.isEmpty()) {
if
(node !=
null
) {
stack.push(node);
node = node.left;
}
else
{
BinaryTreeNode item = stack.peek();
if
(item.right !=
null
&& !visited.contains(item.right))
node = item.right;
else
{
System.out.print(item.value +
" "
);
visited.add(item);
stack.pop();
}
}
}
}
public
static
void
main(String[] args) {
List<Integer> list1 =
new
ArrayList<Integer>();
List<Integer> list2 =
new
ArrayList<Integer>();
list1.add(
1
);
list1.add(
2
);
list1.add(
4
);
list1.add(
7
);
list1.add(
3
);
list1.add(
5
);
list1.add(
6
);
list1.add(
8
);
list2.add(
4
);
list2.add(
7
);
list2.add(
2
);
list2.add(
1
);
list2.add(
5
);
list2.add(
3
);
list2.add(
8
);
list2.add(
6
);
BinaryTreeNode tree = BinaryTreeNode.Construct(list1, list2);
BinaryTreeNode.preOrderLoop(tree);
System.out.println();
BinaryTreeNode.inOrderLoop(tree);
System.out.println();
BinaryTreeNode.postOrderLoop(tree);
}
}
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本文转自 许大树 51CTO博客，原文链接：http://blog.51cto.com/abelxu/1968112，如需转载请自行联系原作者
