[LeetCode 105] Construct Binary Tree from Preorder and Inorder Traversal

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 ago

    public 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

	}

}

[LeetCode 105] Construct Binary Tree from Preorder and Inorder Traversal

原文：http://blog.csdn.net/ever223/article/details/44625041