根据有序数组构建二叉树

根据一个有序数组，构造一颗二叉搜索树

思路：因为数组有序，所以数组中间节点是该二叉树的根节点，因为二叉树的定义是右子树都大于根节点，左子树都小于根节点，构造完根节点后，分别截取数组的前半段和后半段分别递归构造左子树和右子树

 

package com.rui.microsoft;

public class Test86_BuildBSTByArray {

    public static void main(String[] args) {
        int[] a = {1,2,3,4,5};
        Test86_BuildBSTByArray app = new Test86_BuildBSTByArray();
        Node root = app.build(a, 0, a.length-1);
        System.out.println(root.value);
    }
    
    Node build(int[] a, int start, int end){
        if(start > end) return null;
        int mid = start + (end - start) / 2;
        Node root = new Node(a[mid]);
        root.left = build(a, start, mid - 1);
        root.right = build(a, mid+1,end);
        return root;
    }
    
    static class Node{
        int value;
        Node left;
        Node right;
        Node(int v){
            this.value = v;
        }
    }
}