非递归中序遍历

class Solution {
    public int i = 0;
    public TreeNode buildTree(int[] inorder, int[] postorder) {
        i = postorder.length-1;
        if(inorder == null || postorder == null){
            return null;
        }
        return buildTreeChild(inorder,postorder,0,postorder.length-1);
    }
    public TreeNode buildTreeChild(int[] inorder,int[] postorder,
    int inbegin,int inend){
        if(inbegin > inend){
            return null;
        }
        TreeNode root = new TreeNode(postorder[i]);
        //逗号写成了点号，一定要注意细节
        int rootIndex = findIndex(inorder,inbegin,inend,postorder[i]);
        i--;
        root.right = buildTreeChild(inorder,postorder,rootIndex + 1,inend);
        root.left = buildTreeChild(inorder,postorder,inbegin,rootIndex - 1);
        return root;
    }
    public int findIndex(int[] inorder,int begin,int inend,int key){
        for(int i =begin;i<= inend;i++){
            if(inorder[i] == key){
                return i;
            }
        }
        return -1;
    }
}