// @Title: 推理二叉树 (推理二叉树)
// @Author: qisiii
// @Date: 2022-02-19 19:08:33
// @Runtime: 15 ms
// @Memory: 82.1 MB
// @comment: 节省空间
// @flag: ORANGE
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode buildTree(int[] preorder, int[] inorder) {
        if (preorder.length<=0){
            return null;
        }
        int index=0;
        TreeNode root = new TreeNode(preorder[0]);
        for (int i = 0; i < inorder.length&&inorder.length>1; i++) {
            if (inorder[i]==Integer.valueOf(root.val)) {
                index=i;break;
            }
        }
        root.left = buildTree(Arrays.copyOfRange(preorder,1,index+1),Arrays.copyOfRange(inorder,0,index));
        root.right = buildTree(Arrays.copyOfRange(preorder,index+1,preorder.length),Arrays.copyOfRange(inorder,index+1,inorder.length));
        return root;
    }
}

// @Title: 推理二叉树 (推理二叉树)
// @Author: qisiii
// @Date: 2022-02-19 18:33:49
// @Runtime: 9 ms
// @Memory: 85.8 MB
// @comment: 
// @flag: 
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
     public TreeNode buildTree(int[] preorder, int[] inorder) {
        int n = preorder.length;
        if (n == 0)
            return null;
        int rootVal = preorder[0], rootIndex = 0;
        for (int i = 0; i < n; i++) {
            if (inorder[i] == rootVal) {
                rootIndex = i;
                break;
            }
        }
        TreeNode root = new TreeNode(rootVal);
        root.left = buildTree(Arrays.copyOfRange(preorder, 1, 1 + rootIndex), Arrays.copyOfRange(inorder, 0, rootIndex));
        root.right = buildTree(Arrays.copyOfRange(preorder, 1 + rootIndex, n), Arrays.copyOfRange(inorder, rootIndex + 1, n));

        return root;
    }
}

// @Title: 推理二叉树 (推理二叉树)
// @Author: qisiii
// @Date: 2022-02-19 19:01:43
// @Runtime: 81 ms
// @Memory: 41.4 MB
// @comment: 通过递归
// @flag: BLUE
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode buildTree(int[] preorder, int[] inorder) {
       if (preorder.length<=0){
            return null;
        }
        List<Integer> pre=new ArrayList<>();
        for (int i : preorder) {
            pre.add(i);
        }
        List<Integer> in=new ArrayList<>();
        for (int i : inorder) {
            in.add(i);
        }
        return build(pre,in);
    }

    public static TreeNode build(List pre, List in) {
        if (pre.size()<=0){
          return null;
      }
        TreeNode root = new TreeNode((Integer) pre.get(0));
        for (int i = 0; i < in.size()&&in.size()>1; i++) {
            if (in.get(i).equals(Integer.valueOf(root.val))) {
                root.left = build(pre.subList(1, 1 + i), in.subList(0, i));
                root.right = build(pre.subList(1 + i, pre.size()), in.subList(i + 1, in.size()));
            }
        }
        return root;
    }
}