【微軟面試題】在二叉搜尋樹中找最小的大於某個key值的節點

在二叉搜尋樹中找最小的大於某個key值的節點

如
         8
      /       \

   6         12
  /             /   \
2          11    14

key = 8 返回11
key = 1 返回2
key = 16 返回NULL

struct TreeNode{int val;TreeNode* left;TreeNode* right;};// 迭代實現TreeNode * FindCeiling(TreeNode *root, int key){TreeNode * ceiling = NULL;TreeNode * current = root;while(current){if(current->val > key)current = current->left;else{ceiling = current;current = current->right;}}return ceiling;}// 遞迴實現TreeNode * FindCeiling(TreeNode *root, int key){if(root == NULL)return NULL;if(root->val <= key)return FindCeiling(root->right, key);else{TreeNode *ceiling = FindCeiling(root->left, key);return ceiling ? ceiling : root;}}