二叉树掌握的并不好
转方法：
public class Solution {
public TreeNode reConstructBinaryTree(int [] pre,int [] in) {
TreeNode root = reConstructBinaryTree(pre, 0, pre.length-1, in, 0, in.length-1);
return root;
}
public TreeNode reConstructBinaryTree(int [] pre, int startpre, int endpre, int [] in, int startin, int endin) {
if(startpre > endpre || startin>endin)
return null;
TreeNode root = new TreeNode(pre[startpre]);
for(int i = startin; i <= endin; i++){
if(in[i] == pre[startpre]){
root.left = reConstructBinaryTree(pre, startpre+1, startpre+i-startin, in, startin, i-1);
root.right = reConstructBinaryTree(pre, i-startin+startpre+1, endpre, in, i+1, endin);
break;
}
} return root;
}
}