leetcode-783. 二叉搜索树节点最小距离

783. 二叉搜索树节点最小距离

class Solution {
    int ans = Integer.MAX_VALUE;
    List<Integer> list = new ArrayList<>();
    public int minDiffInBST(TreeNode root) {
        dfs(root);
        for(int i = 1; i < list.size(); i++){
            ans = Math.min(ans, list.get(i) - list.get(i-1));
        }
        return ans == Integer.MAX_VALUE ? 0 : ans;
    }

    public void dfs(TreeNode root){
        if(root == null){
            return;
        }

        if(root.left != null){
            dfs(root.left);
        }
        
        list.add(root.val);

        if(root.right != null){
            dfs(root.right);
        }
    }
}