leetcode——105. 从前序与中序遍历序列构造二叉树

这道题做得比较顺利，但是效果并不是很好

public TreeNode buildTree(int[] preorder, int[] inorder) {
        if(preorder.length == 0){
            return null;
        }
        if(preorder.length == 1){
            return new TreeNode(preorder[0]);
        }else{
            int m = 0;
            TreeNode root = new TreeNode(preorder[0]);
            for(int i = 0;i<inorder.length;i++){
                if(inorder[i] == preorder[0]){
                    m = i;   //在中序遍历中找到根节点的位置
                    break;
                }
            }
            int[] a = Arrays.copyOfRange(inorder,0,m);
            int[] b = Arrays.copyOfRange(inorder,m+1,inorder.length);
            int[] c = Arrays.copyOfRange(preorder,1,1+m);
            int[] d = Arrays.copyOfRange(preorder,m+1,preorder.length);
            root.left = buildTree(c,a);
            root.right = buildTree(d,b);
            return root;
        }