二叉树初始化代码

 

struct TreeNode {
  int val;
  TreeNode *left;
  TreeNode *right;
  TreeNode() : val(0), left(nullptr), right(nullptr) {}
  TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
  TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};
 
TreeNode* initBTree(int elements[], int size)
{

    if (size < 1)
    {
        return NULL;
    }
    cout << "开始创建" << endl;
    //动态申请size大小的指针数组
    TreeNode** nodes = new TreeNode * [size];
    //将int数据转换为TreeNode节点
    for (int i = 0; i < size; i++)
    {
        if (elements[i] == 0)
        {
            nodes[i] = nullptr;
        }
        else
        {
            nodes[i] = new TreeNode(elements[i]);
        }
    }
    queue<TreeNode*> nodeQueue;
    nodeQueue.push(nodes[0]);

    TreeNode* node;
    int index = 1;
    while (index < size)
    {
      /*  node = nodeQueue.front();
        nodeQueue.pop();
        nodeQueue.push(nodes[index++]);
        node->left = nodeQueue.back();
        nodeQueue.push(nodes[index++]);
        node->right = nodeQueue.back();*/

        node = nodeQueue.front();
        nodeQueue.pop();
        TreeNode* lnode= nodes[index++];
        if(lnode!=nullptr) nodeQueue.push(lnode);
        node->left = lnode;

        TreeNode* rnode = nodes[index++];
        if (rnode != nullptr) nodeQueue.push(rnode);
        node->right = rnode;
    }
    return nodes[0];
}