java

Code

class Solution {
    public TreeNode createBinaryTree(int[][] descriptions) {
        TreeNode[] map = new TreeNode[100001];
        boolean[] child = new boolean[100001];

        for (int[] d : descriptions) {
            if (map[d[0]] == null)
                map[d[0]] = new TreeNode(d[0]);
            TreeNode node = (map[d[1]] == null ? new TreeNode(d[1]) : map[d[1]]);
            if (d[2] == 1)
                map[d[0]].left = node;
            else
                map[d[0]].right = node;
            map[node.val] = node;
            child[d[1]] = true;
        }

        for (int[] d : descriptions)
            if (!child[d[0]])
                return map[d[0]];

        return null;
    }
}