思路
将中序数组按照下标i划分两部分,左子树的前序下标为1,...,i,右子树前序下标为i+1,...,length-1。
代码
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
import java.util.Arrays;
public class Solution {
public TreeNode reConstructBinaryTree(int [] pre,int [] in) {
if(pre.length == 0 || in.length == 0) return null;
TreeNode root = new TreeNode(pre[0]);
for(int i = 0; i < in.length; i++) {
if(in[i] == pre[0]) {
root.left = reConstructBinaryTree(Arrays.copyOfRange(pre,1,i+1), Arrays.copyOfRange(in,0,i));
root.right = reConstructBinaryTree(Arrays.copyOfRange(pre,i+1,pre.length), Arrays.copyOfRange(in,i+1,in.length));
break;
}
}
return root;
}
}
笔记
copyOfRange函数参数取值左闭右开。