构造二叉树

TreeNode的实现同LeetCode。

public class TreeNode {
    Integer val;
    TreeNode left;
    TreeNode right;
    //TreeNode(Integer x) { val = x; }
    TreeNode(int x) {
        val = x;
        left=null;
        right=null;
    }
}

使用整形数组构造二叉树：

public TreeNode buildTree(Integer[] array){
        TreeNode root=new TreeNode(array[0]);//假设array[0]不为null
        Queue<TreeNode> queue=new LinkedList<TreeNode>();
        queue.offer(root);
        int count=0,len=array.length;
        //System.out.println(len);
        while(!queue.isEmpty()){
            TreeNode temp=queue.poll();
            if(temp!=null){
                if(count+1<len){
                    if(array[count+1]==null)//如果TreeNode的构造函数接收的参数为Integer，则可以省去此处if else
                        temp.left=null;
                    else
                        temp.left=new TreeNode(array[count+1]);
                    count++;
                    queue.offer(temp.left);
                }
                if(count+1<len) {
                    if(array[count+1]==null)
                        temp.right=null;
                    else
                        temp.right = new TreeNode(array[count+1]);
                    count++;
                    queue.offer(temp.right);
                }
            }
        }
        return root;
    }