题解 | #重建二叉树#

/**
 * 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 [] vin) {
        return reConstructBinaryTree(pre,0,pre.length-1,vin,0,vin.length-1);
    }
    private TreeNode reConstructBinaryTree(int[] pre,int startPre,int endPre,int[] in,int startIn,int endIn){
        if(startPre>endPre||startIn>endIn) return null;
        TreeNode root=new TreeNode(pre[startPre]);
        for(int i=startIn;i<=endIn;i++){
            if(in[i]==pre[startPre]){
                root.left=reConstructBinaryTree(pre,startPre+1,startPre+i-startIn,in,startIn,i-1);
                root.right=reConstructBinaryTree(pre,i-startIn+startPre+1,endPre,in,i+1,endIn);
                break;
            }
        }
        return root;
    }
}