二叉树的构建

使用数组构建一颗二叉树

TreeNode[] treeArrays = new TreeNode[10];
  for (int i = 0; i < treeArrays.length; i++) {
    treeArrays[i] = new TreeNode();
    treeArrays[i].val = i;
  }
  //build tree
  int length = treeArrays.length;
  for (int i = 0; i < length; i++) {
      if (2 * i + 1 < length) {
          treeArrays[i].left = treeArrays[2 * i + 1];
      }
      if (2 * i + 2 < length) {
          treeArrays[i].right = treeArrays[2 * i + 2];
      }
  }


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;
    }
}