问题：
给你一个 BST的pre-order / post-order array， reconstruct 出这个BST
pre-order
private int counter_Pre = 0;
public TreeNode restoreBST_Pre(int[] nums) {
return helper_Pre(nums, Integer.MIN_VALUE, Integer.MAX_VALUE);
}
private TreeNode helper_Pre(int[] nums, int min, int max) {
if (counter_Pre >= nums.length) {
return null;
}
int val = nums[counter_Pre];
if (val > min && val < max) {
counter_Pre++;
TreeNode root = new TreeNode(val);
root.left = helper_Pre(nums, min, val);
root.right = helper_Pre(nums, val, max);
return root;
}
return null;
}
post-order
int counter_Post;
public TreeNode restoreBST_Post(int[] nums) {
counter_Post = nums.length - 1;
return helper_Post(nums, Integer.MIN_VALUE, Integer.MAX_VALUE);
}
private TreeNode helper_Post(int[] nums, int min, int max) {
if (counter_Post < 0) {
return null;
}
int val = nums[counter_Post];
if (min < val && val < max) {
counter_Post--;
TreeNode root = new TreeNode(val);
root.right = helper_Post(nums, val, max);
root.left = helper_Post(nums, min, val);
return root;
}
return null;
}
Anyway, Good luck, Richardo! -- 09/23/2016
