LeetCode530. 二叉搜索树的最小绝对差

思路

看到二叉搜索树，就要想到他的中序遍历是递增数列。

然后这道题就很简单了。

代码

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int getMinimumDifference(TreeNode root) {
        if(root == null){
            return 0;
        }
        List<Integer> list = new ArrayList<>();
        fun(root,list);
        int min = Integer.MAX_VALUE;
        int length = list.size();
        for(int i =0,j = i+1;i<length-1;i++,j++){
            min = Math.min(min,Math.abs(list.get(i)-list.get(j)));
        }
        return min;
    }
    public void fun(TreeNode root,List list){
        if(root == null){
            return;
        }
        if(root.left != null){
            fun(root.left,list);
        }
        list.add(root.val);
        if(root.right != null){
            fun(root.right,list);
        }
        
    }
}