使用栈遍历二叉树

二叉树的遍历

先序遍历二叉树

 LinkedList<Integer> stack = new LinkedList<>();

 BinaryTree<String> binaryTree = new BinaryTree<>(
         new String[]{"A", "B", "C", "D", "E", "F", "G"});
 System.out.println(binaryTree);
 int root = binaryTree.root();

 while (root > -1 || !stack.isEmpty()) {
     //先访问左子树,并且入栈
     while (root > -1) {
         String value = binaryTree.get(root);
         print(value);
         stack.push(root);
         root = binaryTree.left(root);
     }
     //处理右子树
     if (!stack.isEmpty()) {
         root = stack.pop();
         root = binaryTree.right(root);
     }

 }

A
BC
DEFG

ABDECFG

中序遍历二叉树

 LinkedList<Integer> stack = new LinkedList<>();

 BinaryTree<String> binaryTree = new BinaryTree<>(
         new String[]{"A", "B", "C", "D", "E", "F", "G"});
 System.out.println(binaryTree);
 int root = binaryTree.root();
 while (root > -1 || !stack.isEmpty()) {
     //先左子树入栈
     while (root > -1) {
         stack.push(root);
         root = binaryTree.left(root);
     }
     //访问,处理右子树
     if (!stack.isEmpty()) {
         root = stack.pop();
         String value = binaryTree.get(root);
         print(value);
         root = binaryTree.right(root);
     }
 }

A
BC
DEFG

DBEAFCG

后序遍历二叉树

 LinkedList<Integer> stack = new LinkedList<>();

 BinaryTree<String> binaryTree = new BinaryTree<>(
         new String[]{"A", "B", "C", "D", "E", "F", "G"});
 System.out.println(binaryTree);
 int root = binaryTree.root();
 int lastAccess = Integer.MAX_VALUE;
 while (root > -1 || !stack.isEmpty()) {
     //先左子树入栈
     while (root > -1) {
         stack.push(root);
         root = binaryTree.left(root);
     }
     root = stack.peek();
     int right = binaryTree.right(root);
     //没有右子树访问,出栈
     if (right == -1 || right == lastAccess) {
         lastAccess = root;
         String value = binaryTree.get(root);
         print(value);
         stack.pop();
         root = -1;
     } else {
         root = right;
     }
 }

A
BC
DEFG

DEBFGCA

引用

• 源码