Question

我正在尝试使用路径压缩算法实现快速联合，由于某种原因，我在测试时遇到了TypeError: 'builtin_function_or_method' object is not subscriptable。对我来说一切都很好。这是代码；感谢您的帮助。

这是完整的错误，后跟代码：

Traceback (most recent call last):
  File "quick-find.py", line 75, in <module>
    a.union(7,9)
  File "quick-find.py", line 56, in union
    node2_root = self.root(node2)
  File "quick-find.py", line 47, in root
    self.id[node] = self.id[id[node]]
TypeError: 'builtin_function_or_method' object is not subscriptable

class weightedQuickUnion:
    def __init__(self, n):
        self.id = list(range(n))
        self.size = list([1]) * n

    def root( self, node ):
        # Improved to make every node point to its parent
            # This improvement makes it weightedQuickUnionWithPathCompression
        while ( node != self.id[node]):
            self.id[node] = self.id[id[node]]
            node = self.id[node]
        return node

    def connected(self, node1, node2):
        return self.id[node1] == self.id[node2]

    def union(self, node1, node2):
        node1_root = self.root(node1)
        node2_root = self.root(node2)
        if node1_root == node2_root:
            return
        if (self.size[node1_root] < self.size[node2_root]):
            self.id[node1_root] = node2_root
            self.size[node2_root] += self.size[node1_root]
        else:
            self.id[node2_root] = node1_root
            self.size[node1_root] += self.size[node2_root]

a = weightedQuickUnion(10)
print(a.id)
print(a.size)
print(a.connected(3,4))
a.union(3,4)
a.union(1,3)
a.union(6,9) 
print(a.id)
print(a.size)
a.union(7,9) # <-- this line throws an exception and I can't figure out why.
a.union(8,9)

Answer 1

感谢@jasonharper指出我放弃了“自我”。从以下行：

// Copyright 2018 The Flutter team. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/material.dart';
import 'package:english_words/english_words.dart';

void main() => runApp(MyApp());

// #docregion MyApp
class MyApp extends StatelessWidget {
  // #docregion build
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Startup Name Generator',
      theme: ThemeData(
        primaryColor: Colors.white,
      ),
      home: RandomWords(),
    );
  }
  // #enddocregion build
}
// #enddocregion MyApp

// #docregion RWS-var
class RandomWordsState extends State<RandomWords> {
  final _suggestions = <WordPair>[];
  final Set<WordPair> _saved = Set<WordPair>();
  final _biggerFont = const TextStyle(fontSize: 18.0);
  // #enddocregion RWS-var

  // #docregion _buildSuggestions
  Widget _buildSuggestions() {
    return ListView.builder(
        padding: const EdgeInsets.all(16.0),
        itemBuilder: /*1*/ (context, i) {
          if (i.isOdd) return Divider(); /*2*/

          final index = i ~/ 2; /*3*/
          if (index >= _suggestions.length) {
            _suggestions.addAll(generateWordPairs().take(10)); /*4*/
          }
          return _buildRow(_suggestions[index]);
        });
  }
  // #enddocregion _buildSuggestions

  // #docregion _buildRow
  Widget _buildRow(WordPair pair) {
    final bool alreadySaved = _saved.contains(pair);
    return ListTile(
      title: Text(
        pair.asPascalCase,
        style: _biggerFont,
      ),
      trailing: Icon(
        alreadySaved ? Icons.favorite : Icons.favorite_border,
        color: alreadySaved ? Colors.red : null,
      ),
      onTap: () {
        setState(() {
          if (alreadySaved) {
            _saved.remove(pair);
          } else {
            _saved.add(pair);
          }
        });
      },
    );
  }
  // #enddocregion _buildRow

  // #docregion RWS-build
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Startup Name Generator'),
        actions: <Widget>[
          IconButton(icon: Icon(Icons.list), onPressed: _pushSaved),
        ],
      ),
      body: _buildSuggestions(),
    );
  }
  // #enddocregion RWS-build

  void _pushSaved() {
    Navigator.of(context).push(
      MaterialPageRoute<void>(
        // Add 20 lines from here...
        builder: (BuildContext context) {
          final Iterable<ListTile> tiles = _saved.map(
            (WordPair pair) {
              return ListTile(
                title: Text(
                  pair.asPascalCase,
                  style: _biggerFont,
                ),
              );
            },
          );
          final List<Widget> divided = ListTile.divideTiles(
            context: context,
            tiles: tiles,
          ).toList();

          return Scaffold(
            appBar: AppBar(
              title: Text('Saved Suggestions'),
            ),
            body: ListView(children: divided),
          );
        },
      ),
    );
  }
  // #docregion RWS-var
}
// #enddocregion RWS-var

class RandomWords extends StatefulWidget {
  @override
  RandomWordsState createState() => RandomWordsState();
}

应该是这样：

self.id[node] = self.id[id[node]]

实现Union-Find，获取TypeError：“ builtin_function_or_method”对象不可下标

1 个答案: