Minimum Absolute Difference in BST

最新推荐文章于 2018-01-11 15:22:31 发布

原创最新推荐文章于 2018-01-11 15:22:31 发布 · 195 阅读

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本文介绍了一种算法，用于找到二叉搜索树中任意两节点间最小绝对值差的方法。通过迭代遍历的方式，利用栈来辅助，实现对二叉树节点的访问，并记录最小差异。

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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:

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
    int getMinimumDifference(TreeNode* root) {
        int res = INT_MAX, pre = -1;
        stack<TreeNode*> s;
        TreeNode *p = root;
        while (p || !s.empty()) {
            while (p) {
                s.push(p);
                p = p->left;
            }
            p = s.top(); s.pop();
            if (pre != -1) res = min(res, p->val - pre);
            pre = p->val;
            p = p->right;
        }
        return res;
    }
};