// 二叉樹結點的描述  typedef struct BiTNode  {      char data;      struct BiTNode *lchild, *rchild;      // 左右孩子  }BinaryTreeNode; // 節點只有左指標、右指標，沒有parent指標，root已知BinaryTreeNode* findLowestCommonAncestor(BinaryTreeNode* root , BinaryTreeNode* a , BinaryTreeNode* b){ if(root == NULL)  return NULL; if(root == a || root == b)  return
 
 root; BinaryTreeNode* left = findLowestCommonAncestor(root->lchild , a , b); BinaryTreeNode* right = findLowestCommonAncestor(root->rchild , a , b); if(left && right)  return root; return left ? left : right;}

// 二叉樹是個二叉查詢樹，且root和兩個節點的值(a, b)已知BinaryTreeNode* findLowestCommonAncestor
 
(BinaryTreeNode* root , BinaryTreeNode* a , BinaryTreeNode* b){ char min  , max; if(a->data < b->data)  min = a->data , max = b->data; else  min = b->data , max = a->data; while(root) {  if(root->data >= min && root->data <= max)   return root;  else if(root->data < min && root->data < max)   root = root->rchild;  else   root = root->lchild; } return NULL;}