题解 | #牛群的树形结构重建#
牛群的树形结构重建
https://www.nowcoder.com/practice/bcabc826e1664316b42797aff48e5153
import java.util.*; /* * public class TreeNode { * int val = 0; * TreeNode left = null; * TreeNode right = null; * public TreeNode(int val) { * this.val = val; * } * } */ public class Solution { /** * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可 * * * @param inOrder int整型一维数组 * @param postOrder int整型一维数组 * @return TreeNode类 */ public TreeNode buildTree (int[] inOrder, int[] postOrder) { // write code here if(inOrder.length ==0){ return null; } int rootVal = postOrder[postOrder.length -1]; TreeNode result = new TreeNode(rootVal); int index = findRootIndex(inOrder,rootVal); TreeNode left = buildTree(Arrays.copyOfRange(inOrder,0,index),Arrays.copyOfRange(postOrder,0,index)); TreeNode right = buildTree(Arrays.copyOfRange(inOrder, index + 1,inOrder.length),Arrays.copyOfRange(postOrder,index,postOrder.length-1)); result.left = left; result.right = right; return result; } public int findRootIndex(int[] arr,int rootVal){ for(int i = 0; i < arr.length;i++){ if(arr[i] == rootVal){ return i; } } return -1; } }