package LeetCode;

import java.util.HashMap;

public class LC_105 {
    public static class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode() {
        }

        TreeNode(int val) {
            this.val = val;
        }

        TreeNode(int val, TreeNode left, TreeNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }

    static HashMap<Integer, Integer> map = new HashMap<>();

    public static TreeNode buildTree(int[] preorder, int[] inorder) {

        for (int i = 0; i < inorder.length; i++) {
            map.put(inorder[i], i);
        }
        int len = preorder.length;
        return Tree(preorder, inorder, 0, len - 1, 0, len - 1);
    }

    public static TreeNode Tree(int[] preorder, int[] inorder, int preorder_Left, int preorder_Right, int inorder_Left, int inorder_Right) {
        if (preorder_Left > preorder_Right) return null;
        int inorder_root = map.get(preorder[preorder_Left]);
        int sizeLeft = inorder_root - inorder_Left;


        TreeNode root = new TreeNode(preorder[preorder_Left]);
        root.left = Tree(preorder, inorder, preorder_Left + 1, preorder_Left + sizeLeft, inorder_Left, inorder_root - 1);
        root.right = Tree(preorder, inorder, preorder_Left + sizeLeft + 1, preorder_Right, inorder_root + 1, inorder_Right);
        return root;
    }
}