[LeetCode] 530. Minimum Absolute Difference in BST

轉自LeetCode

Given a binary search tree with non-negative values, find the minimum absolute difference between values of any two nodes.

Example:

Input:

   1
    \
     3
    /
   2

Output:
1

Explanation:
The minimum absolute difference is 1, which is the difference between 2 and 1 (or between 2 and 3).

Note: There are at least two nodes in this BST.

<Solution>

想法如下

• 因為是BST，所以用 inorder traversal 會得到一個由小到大的數列。因此，在歷遍的時候，檢查當下的值減掉前面的值，並記錄最小的差距，歷遍結束後就會得到答案。這是因為數列是排序的，最小值一定是兩個相鄰的數相減來得到的

code 如下

C++(使用遞迴)

Java(使用 stack)