题目描述
输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。
/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
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;
}
private TreeNode reConstructBinaryTree(int[] pre, int startPre, int endPre, int[] in, int startIn, int endIn){
if(startPre>endPre || startIn>endIn){
return null;
}
TreeNode node = new TreeNode(pre[startPre]);
for(int i=startIn; i<=endIn; i++){
//找根节点
if(in[i] == pre[startPre]){
node.left = reConstructBinaryTree(pre, startPre+1, i-startIn+startPre, in, startIn, i-1);
node.right = reConstructBinaryTree(pre, i-startIn+startPre+1, endPre, in, i+1, endIn);
break;
}
}
return node;
}
}
