[LeetCode 105]Construct Binary Tree from Preorder and Inorde

题目链接：construct-binary-tree-from-preorder-and-inorder-traversal

import java.util.Arrays;//根据前序和中序遍历构建二叉树/** * Given preorder and inorder traversal of a tree, construct the binary tree.Note:You may assume that duplicates do not exist in the tree. * */public class ConstructBinaryTreeFromPreorderAndInorderTraversal {public class TreeNode {int val;TreeNode left;TreeNode right;TreeNode(int x) {val = x;}}//202 / 202 test cases passed.//Status: Accepted//Runtime: 380 ms//Submitted: 0 minutes agopublic TreeNode buildTree(int[] preorder, int[] inorder) {int len = preorder.length;if(len > 0) {TreeNode root = new TreeNode(preorder[0]);int rootIndex = 0;//找到根节点在中序遍历中的位置for(; rootIndex < len; rootIndex++) {if(inorder[rootIndex] == preorder[0]) {break;}}//分别构建左右子树root.left = buildTree(Arrays.copyOfRange(preorder, 1, 1 + rootIndex),Arrays.copyOfRange(inorder, 0, rootIndex));root.right = buildTree(Arrays.copyOfRange(preorder, rootIndex + 1, len),Arrays.copyOfRange(inorder, rootIndex + 1, len));return root;}else {return null;}}public static void main(String[] args) {// TODO Auto-generated method stub}}

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