LeetCode：M-105. Construct Binary Tree from Preorder and Inorder Traversal

LeetCode链接

Given preorder and inorder traversal of a tree, construct the binary tree.

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */class Solution {    public TreeNode buildTree(int[] preorder, int[] inorder) {        return sub(preorder, inorder, 0, 0, preorder.length-1);    }    int findIndex(int label, int[] inorder, int ins, int ine){        for(int i=ins; i<=ine; i++){            if(label==inorder[i])                return i;        }                return -1;    }        TreeNode sub(int[] preorder, int[] inorder, int index, int ins, int ine){                if(ins>ine)            return null;                int label = preorder[index];        int centerIndex = findIndex(label, inorder, ins, ine);                TreeNode left = sub(preorder, inorder, index+1, ins, centerIndex-1);        TreeNode right = sub(preorder, inorder, index+(centerIndex-ins)+1, centerIndex+1, ine);                TreeNode node = new TreeNode(label);        node.left = left;        node.right = right;                return node;    }}