530. Minimum Absolute Difference in BST二叉搜索树-优快云博客

本文链接：https://blog.youkuaiyun.com/jianingkid/article/details/75330308

本文介绍了一种算法，用于查找二叉搜索树中任意两节点间最小绝对差值的方法。通过遍历树并利用其特性进行优化，确保了高效求解。

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.

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    
    
    public int getMinimumDifference(TreeNode root) {
        if(root==null)return 0;
        int min=Integer.MAX_VALUE;
        Queue<TreeNode> a=new LinkedList<>();
        List<Integer> b=new ArrayList<>();
        a.add(root);
        b.add(root.val);
        while(!a.isEmpty()){
            int n=a.size();
            for(int i=0;i<n;i++){
                TreeNode p=a.poll();
                if(p.left!=null){
                    a.add(p.left);
                    //min=Math.abs(p.val-p.left.val)<min?Math.abs(p.val-p.left.val):min;
                    b.add(p.left.val);
                }
                if(p.right!=null){
                    a.add(p.right);
                    //min=Math.abs(p.val-p.right.val)<min?Math.abs(p.val-p.right.val):min;
                    b.add(p.right.val);
                }
            }
        }
        Collections.sort(b);
        Integer[] c=b.toArray(new Integer[b.size()]);
        for(int i=0;i<c.length-1;i++){
            min=c[i+1]-c[i]<min?c[i+1]-c[i]:min;
        }
        return min;
    }
}

利用二叉搜索树本身的特性

public class Solution {
    int min = Integer.MAX_VALUE;
    Integer prev = null;
    
    public int getMinimumDifference(TreeNode root) {
        if (root == null) return min;
        
        getMinimumDifference(root.left);
        
        if (prev != null) {
            min = Math.min(min, root.val - prev);
        }
        prev = root.val;
        
        getMinimumDifference(root.right);
        
        return min;
    }
    
}