leetcode——99.恢复二叉搜索树

public void recoverTree(TreeNode root) {
        ArrayList<Integer> result = inOrder(root);
        int[] a = result.stream().mapToInt(Integer::valueOf).toArray();
        int[] b = Arrays.copyOf(a,a.length);//b是原始顺序
        Arrays.sort(a);//a是排序好的
        //经过比较可找出是哪两个数字进行了位置交换
        int m = MAX_VALUE,n = m;
        for(int i = 0;i<a.length;i++){
            if(b[i] != a[i]){
                m = b[i];
                n = a[i]; //找到了交换了的两个数值
                break;
            }
        }
        //遍历树，找到对应节点，进行交换
        inSearch(m,n,root);
    }

    private void inSearch(int m, int n,TreeNode node) {
        if(node == null){
            return;
        }else{
            inSearch(m, n, node.left);
            if(node.val == m){
                node.val = n;
            }else if(node.val == n){
                node.val = m;
            }
            inSearch(m,n,node.right);
        }
    }

    ArrayList<Integer> list = new ArrayList<>();
    private ArrayList<Integer> inOrder(TreeNode node){
        if(node == null){
            return list;
        }else {
            inOrder(node.left);
            list.add(node.val);
            inOrder(node.right);
        }
        return list;
    }