重建二叉树

重建二叉树

public TreeNode reConstructBinaryTree(int [] pre, int [] in) {
    return reConstructBinaryTree(pre,in,0,pre.length-1,0,in.length-1);
}

private TreeNode reConstructBinaryTree(int[] pre,int[] in,
                                       int preStart,int preEnd,
                                       int inStart,int inEnd){
    if(preStart>preEnd || inStart>inEnd){
        return null;
    }
    TreeNode root = new TreeNode(pre[preStart]);

    int index = -1;
    for(int i=inStart;i<=inEnd;i++){
        if(in[i]==pre[preStart]){
            index = i;
            break;
        }
    }
    root.left = reConstructBinaryTree(pre,in,
                                      preStart+1,preStart+(index-inStart),inStart,index-1);
    root.right = reConstructBinaryTree(pre,in,
                                       preStart+(index-inStart)+1,preEnd,index+1,inEnd);
    return root;
}

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