Convert Sorted Array to Binary Search Tree

给一个sorted数组, 建立一个bst.

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode sortedArrayToBST(int[] nums) {
        return rec(nums, 0, nums.length - 1);
    }
    public TreeNode rec (int[] nums, int start, int end) {
        if(start > end)
            return null;
        int mid = start + (end - start) / 2;
        TreeNode root = new TreeNode(nums[mid]);
        root.left = rec(nums,start,mid-1);
        root.right = rec(nums,mid+1, end);
        return root;
    }
}

/**

* Definition for a binary tree node.

* public class TreeNode {

* int val;

* TreeNode left;

* TreeNode right;

* TreeNode(int x) { val = x; }

* }

public class Solution {

public TreeNode sortedArrayToBST(int[] nums) {

return rec(nums, 0, nums.length - 1);

}

public TreeNode rec (int[] nums, int start, int end) {

if(start > end)

return null;

int mid = start + (end - start) / 2;

TreeNode root = new TreeNode(nums[mid]);

root.left = rec(nums,start,mid-1);

root.right = rec(nums,mid+1, end);

return root;

}

Convert Sorted Array to Binary Search Tree

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这青苔碧瓦堆, 俺曾睡风流觉, 将五十年兴亡看饱.

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