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
中序遍历
Code
class Solution {
Integer res = Integer.MAX_VALUE, pre = null;
public int getMinimumDifference(TreeNode root) {
if (root.left != null) {
getMinimumDifference(root.left);
}
if (pre != null) res = Math.min(res, root.val - pre);
pre = root.val;
if (root.right != null) {
getMinimumDifference(root.right);
}
return res;
}
}
class Solution {
public int getMinimumDifference(TreeNode root) {
int res = Integer.MAX_VALUE;
Stack<TreeNode> stack = new Stack<>();
TreeNode cur = root;
TreeNode pre = null;
while (cur != null || !stack.isEmpty()) {
while (cur != null) {
stack.push(cur);
cur = cur.left;
}
cur = stack.pop();
if (pre != null) {
res = Math.min(res, cur.val - pre.val);
}
pre = cur;
cur = cur.right;
}
return res;
}
}