public static TreeNode createTree(int index,int[] arr){
if(index>=arr.length){
return null;
}
TreeNode root = new TreeNode();
root.val = arr[index];
root.left = createTree(index*2+1,arr);
root.right = createTree(index*2+2,arr);
return root;
}
static class TreeNode{
public TreeNode left;
public TreeNode right;
public Integer val;
public TreeNode(){
}
}
后序遍历下
public static void afterOrder(TreeNode root){
TreeNode prev = null;
Stack s = new Stack<>();
while(root!=null || !s.empty()){
while (root!=null){
s.add(root);
root = root.left;
}
root = s.pop();
if(root.right==null || root.right==prev){
System.out.print(root.val+" ");
prev = root;
root = null;
}else{
s.add(root);
root = root.right;
}
}
}
调用创建二叉树方法
public static void main(String[] args) {
int[] arr = new int[]{1,2,3,4,5,6};
TreeNode tree = createTree(0, arr);
afterOrder(tree);
}
打印
4 5 2 6 3 1
