Description
Given a binary search tree, write a function kthSmallest to find the kth smallest element in it.
Solution
获取左子树的节点数number 如果左子树节点数刚好为k-1，说明该节点为第k个，否则向左子树找或者向右子树找。
Code
/**
* 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 kthSmallest(TreeNode root,
int k) {
int number = number(root.left);
if (number == k -
1) {
return root.val;
}
else if (number >= k) {
return kthSmallest(root.left, k);
}
else {
return kthSmallest(root.right, k -
1 - number);
}
}
public int number(TreeNode node) {
if (node ==
null) {
return 0;
}
else {
return number(node.left) + number(node.right) +
1;
}
}
}
