H***e
发帖数: 476 | 1 backtracking,就是哪些机器人走路啊，matrix里word路径啊，8皇后等，bst一般不是
backtracking吧。
， |
|
A**u
发帖数: 2458 | 2 backtrack方法
注意优化，去掉不可能的path
我也是比照 这个题目的 比如 递增整数, a1,a2,a3,...,an
求所有组合，使得 它的和=target.
这个就用backtrack
两个题目思路一样。
另外的办法，就是推公式了，不过不显然 |
|
f*********m
发帖数: 726 | 3 能否用backtracking？从左到右每个位置都有机会取值1~9，某一位invalid的条件是根
据这一位前面各位的取值以及D，I情况，这一位小于1或者大于9。若某一位invalid，
则backtrack，前一位取另一个值。
不过麻烦了些。 |
|
c********t
发帖数: 5706 | 4 我也是这么想的。貌似还容易些，不用backtracking. 不过既然不用backtracking,确
实也不一定要recursion了。直接移动-》输出-》移动—》输出，直到单词结束。 |
|
i**********e
发帖数: 1145 | 5 word ladder II 有人过了 large tests 吗？
我抛砖引玉一下吧，希望有大牛可以提出更好的解法。
思路就是按照 wwwyhx 的思路 backtrack 重建路径。昨晚写了一下，果然简洁很多，
整个程序不到50行。
基于程序可读性，所以 bottom up 返回路径，产生了很多不必要的拷贝而导致效率会
差很多。但路径组合没那么多，所以性能上也没什么影响。
typedef unordered_multimap Map;
typedef pair PairIter;
vector> findLadders(string start, string end, unordered_set<
string> &dict) {
Map map, map2;
queue q, q2;
q.push(start);
bool goal = false;
while (!q.empty()) {
... 阅读全帖 |
|
c********t
发帖数: 5706 | 6 看明白了.
1.遍历 构造map
2.由map, backtrack重建pathes
我模仿的写了一个java的，真的过了。1592ms
虽然双queue解法不需要backtracking,但TLE可能还是因为, 要往path queue里面存太
多path吧(每个node都要建一个path)，读写太多了，而这个解法存的是edges(每个node
只用存parent nodes),读写少些。 |
|
i**********e
发帖数: 1145 | 7 word ladder II 有人过了 large tests 吗？
我抛砖引玉一下吧，希望有大牛可以提出更好的解法。
思路就是按照 wwwyhx 的思路 backtrack 重建路径。昨晚写了一下，果然简洁很多，
整个程序不到50行。
基于程序可读性，所以 bottom up 返回路径，产生了很多不必要的拷贝而导致效率会
差很多。但路径组合没那么多，所以性能上也没什么影响。
typedef unordered_multimap Map;
typedef pair PairIter;
vector> findLadders(string start, string end, unordered_set<
string> &dict) {
Map map, map2;
queue q, q2;
q.push(start);
bool goal = false;
while (!q.empty()) {
... 阅读全帖 |
|
c********t
发帖数: 5706 | 8 看明白了.
1.遍历 构造map
2.由map, backtrack重建pathes
我模仿的写了一个java的，真的过了。1592ms
虽然双queue解法不需要backtracking,但TLE可能还是因为, 要往path queue里面存太
多path吧(每个node都要建一个path)，读写太多了，而这个解法存的是edges(每个node
只用存parent nodes),读写少些。 |
|
e******i
发帖数: 106 | 9 这是在career cup 上看到的题：
Given a hashmap M which is a mapping of characters to arrays of substitute
characters, and an input string S, return an array of all possible mutations
of S (where any character in S can be substituted with one of its
substitutes in M, if it exists).
What is the time complexity? What is the space complexity? Can you optimize
either?
Example input:
M = { f: [F, 4], b: [B, 8] }
S = fab
Expected output:
[fab, Fab, 4ab, faB, FaB, 4aB, fa8, Fa8, 4a8]
这是我的解法，用backtrack... 阅读全帖 |
|
d***n
发帖数: 832 | 10 backtracking/DFS加memorization是怎么做的
哪位能不能贴一下code，最好在leetcode解法基础上加memorization的
//我手上只有backtracking的解法和DP的解法 |
|
M*******a
发帖数: 1633 | 11 我老编了个程序验证过了，基本只要一位一位算过去，如果不行就backtracking就行了
，其实需要backtracking的情况很少。
基本只要1003个字符就可以了，而且首尾可以衔接，也就是说一个1000的环就可以了 |
|
n*******s
发帖数: 482 | 12 补充一下 在最后的结果表达式中，数字的顺序随便(但必须k个都用到)，操作符的选择
和顺序随便，括号
的选择随便，但要合法。
楼上说的递归，没错，在这个题目里backtracking本质上就是permutation，不是么.
另外 在无括号的情况下，backtracking求表达式很好写，但是有括号呢？ |
|
b*********n
发帖数: 464 | 13 好像是NP问题http://en.wikipedia.org/wiki/Set_cover_problem
现在能想到的只有backtrack。可以通过下面的方法缩小搜索空间：
1.可以先用geedy得到一个次优解：首先用含有1最多的行，然后一次选取能增加1最多
的行，直到m个1被cover。假设次优解是m1(m1<=m).backtrack最多需要搜索m1层。
2.如果一行被另一行cover，删除这一行。如果有多行相等，只保留一行。
3.如果某一列只有被一行包括，选定这一行，这个在回溯之前做
1 |
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t**r
发帖数: 3428 | 14 走迷宫的 时间复杂度是多少？谢谢 如这个解法
#include
// Maze size
#define N 4
bool solveMazeUtil(int maze[N][N], int x, int y, int sol[N][N]);
/* A utility function to print solution matrix sol[N][N] */
void printSolution(int sol[N][N])
{
for (int i = 0; i < N; i++)
{
for (int j = 0; j < N; j++)
printf(" %d ", sol[i][j]);
printf("n");
}
}
/* A utility function to check if x,y is valid index for N*N maze */
bool isSafe(int maze[N][N], int x, int y)
{
// if (x,y out... 阅读全帖 |
|
b*****n
发帖数: 618 | 15 难道你们真的认为面试官expect你必须用上面de brujin sequence的解法答出来？
不知道你们怎么想的，面试考察的仍然是基本的coding和算法，这个题目不用de
brujin就做不了了吗？
这个题目就是基本的dfs ＋ backtracking，每次试下一个可能的数是什么，不行就
backtrack，然后记录下来所有已经试过的密码是什么就行了 |
|
b*****n
发帖数: 618 | 16 上面一直都在讨论的是BFS，你老一句没头没脑的backtracking，估计根本没仔细看就
找个机会来喷而已，爽了么？
这个题目上面已经说了不能用recursion，所以我猜意思是不能用DFS，而且我确实不懂
backtracking跟我们之前讨论的有什么关系，所以你能不能说说你的解法让我学习一下？ |
|
b*****n
发帖数: 618 | 17 我用backtracking没有你出神入化，感觉做这个题目不如BFS
你上个backtracking的解法吧，看看能不能比BFS更好
你要就是想喷我可以专门开贴，讨论题目就是讨论题目，不欢迎我可以不来。 |
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I******c
发帖数: 163 | 18 我的java实现，参考了Blaze的思路，不过不知道真正理解了他的思路没有，因为我不
太看得懂javascript.下面是几个点：
1. 这个题目用的是backtracking而不是dp，因为dp不可能给你产生排列组合。dp通常
就是给你一个最值。
2. 时间复杂度是指数级。
3. 题目的本质是产生排列。
4. 一般的backtracking来形成字符串的话,从现有字母集中每次任意挑一个字母,然后
从剩下的字母里继续挑。把所有字母都加到字符串里面去了，这轮程序也就完了。这个
题目因为有个顺序的限制条件，决定程序怎样进行下去并不能用剩下多少字符来决定，
而应该是用已经加入字符串的字母的位置来决定。
import java.util.HashMap;
import java.util.List;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Set;
public class Example5 {
public static void main(String [] args){
... 阅读全帖 |
|
x********o
发帖数: 25 | 19 不需要存local copy，只存这个swap，backtrack要revert这个swap回到原来的样子。
前面也说了要两头都check，然后取minimum。
geeksforgeeks 这个算法是O（N）的吗？swap 后对后面的做完递归，就backtrack不了
，除非把swap前的vector保留一个local拷贝，那这样递归函数........ |
|
I******c
发帖数: 163 | 20 leecode上的word search I/II说白了就是backtracking/穷举嘛。这道题也可以用嘛
把每个词在board上的位置记下来（如果这个词存在于board上的话）。然后就
backtracking每个词。如果一个词在board上有多个的可能，那试的时候就把多个可能
都试一下。 |
|
i*********r
发帖数: 5101 | 21 i don't think dolphins can force Wallace for his stance, but as an
organization they have to or better to explain their stance, that's what
they did...
Wallace can say whatever he says, he does not have to backtrack, it is his
choice to backtrack for whatever reasons, I don't think that means he
changed his stance, To be fair, his words was not that bad like anti-gay
hatred etc., more or less shows he does not understand why gay is being gay.
., I am sure here are a lot of people understand him,... 阅读全帖 |
|
A******1
发帖数: 786 | 22 I would like to try a tele.
Maybe my next one will be a tele...
To Kirchhoff
Is the backtrack also from the book?
Will you be able to share the book and backtrack? |
|
t**x
发帖数: 1511 | 23 操作系统：Linux (distribution backtrack 3，google一下就找到了)
按照教程做bootable USB stick:
http://backtrack.offensive-security.com/index.php/Howto:USB_Stick
(so easy, a cave man can do it..)
如果喜欢，可以拆了T60上的硬盘，光驱(现在还找不到T60的光驱槽dummy)
开机进BIOS，改为boot from USB HDD，save changes and exit.
启动之后就自动从USB load起linux了，菜单里面选第一个KDE界面就好。
大概boot time < 20s (菜单到开启firefox浏览)
sound card/wifi/bluetooth/display etc etc. all support by default，不用额外
driver什么的东西。我的机器直接boot起来wifi/bluetooth/sound card正常，14寸屏
1400x1050分辨率也是自动识别了。(T61的需要一个 |
|
p*****c
发帖数: 20445 | 24 Christopher D. Lima, Ph.D.
Memorial Sloan-Kettering Cancer Center
Christopher Lima doesn’t pick easy problems. A structural biologist, he is
investigating how cells attach small proteins—like ubiquitin and the
related molecule SUMO—to other proteins to modify their function or fate.
Alongside those studies, he is exploring the molecular mechanisms that
underlie RNA processing and degradation—modifications to an RNA copy of a
gene that influence its stability and ability to be used as a template ... 阅读全帖 |
|
B*********h
发帖数: 800 | 25 ☆─────────────────────────────────────☆
yingxiang (yingxiang) 于 (Sat Dec 2 00:09:39 2006) 提到:
X和Y对一个7局4胜的A队和B队之间的体育比赛打赌.在每局比赛的开始,由X指定赌金的
多少.如果X赌a元,如果A队赢,则Y付给X a 元,否则X付给Y a元. 现在X希望如果最终 A
队赢,自己可以赚100,如果B队赢,自己输100.问最初的赌金应该设到多少?
☆─────────────────────────────────────☆
mfp (夜曲) 于 (Sat Dec 2 00:52:20 2006) 提到:
31.25? backtracking
☆─────────────────────────────────────☆
lieren (firstblood--pally) 于 (Sat Dec 2 04:52:18 2006) 提到:
我也得到这个答案。
有什么简单的方法嘛？
backtrack 花时间不少啊。
也许是这个树太不好画了，影响观察，呵 |
|
|
c******g
发帖数: 4889 | 27 现在破WEP已经是极其容易了，几分钟就可以，而且软件很容易得到，上面提到的
aircrack，backtrack等。
难的是WAP，要用字典。 |
|
s*****V
发帖数: 21731 | 28 http://www.huffingtonpost.com/2011/11/03/herman-cain-china-nucl
Herman Cain is having a tough week.
On top of struggling to effectively respond to multiple allegations of past
sexual harassment made against him that have resurfaced, Cain stumbled on
foreign policy when he incorrectly claimed China is trying to develop
nuclear capability. In fact, the country's first test on a nuclear device
was back in 1964.
Cain addressed the gaffe in an interview with Ginni Thomas of The Daily
Caller on Wednes... 阅读全帖 |
|
z*****t
发帖数: 1356 | 29 这哥们范了太多的致命错误了：
The Kims had violated a number of rules that would have been familiar to
locals or to experienced backwoodsmen, but perhaps not to them. They had
left too late at night, they had left the main road, and they hadn’t turned
around or tried to back up once it began to snow and their gas tank edged
toward empty. More than once they had forged ahead when they should’ve
backtracked to the known world and safety. |
|
b*****y
发帖数: 547 | 30 The Kim family reportedly missed the exit for Highway 42 just a few miles
south of Roseburg. Instead of backtracking, they kept driving south on I-5,
and then turned off the highway in search of an alternate route across the
Coast Range. Their ultimate goal was something called Bear Camp Road. It
hasn’t yet been officially reported which map the Kims were using, but the
2006 Rand |
|
g**1
发帖数: 10330 | 31 http://www.telegraph.co.uk/news/uknews/immigration/10433691/Bor
Border police storm 'sham' wedding then backtrack when couple appear genuine
Chinese bride Miao Guo and Italian groom Massimo Ciabattini, who met whilst
working at Harrods, were questioned for 30 minutes before they were allowed
back into Camden Town Hall to complete the ceremony
英国边境警察冲入英国一个婚礼现场，怀疑中国新娘miaoguo与意大利新郎假结婚，因
为彼此都不能正确拼出对方名字，但最终证据不足让其完成婚礼。 |
|
g*******y
发帖数: 202 | 32 再比较一下新华网英文网站
http://news.xinhuanet.com/english/world/2013-12/03/c_125802480.
TOKYO, Dec. 3 (Xinhua) -- Japanese Prime Minister Shinzo Abe and U.S. Vice
President Joseph Biden held talks here Tuesday as part of Biden's week-long
trip that will also see him visit China and South Korea at a time when
tensions in the Asia Pacific regions, due to territorial disputes and air
demarkation zones, are rising.
The two leaders jointly told a news conference after their meeting that in a
coordinated effort ... 阅读全帖 |
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f******d
发帖数: 2394 | 33 心虚了？不是告诉你了么中崩元年是2013年。看中国经济就看房价。2013年是顶点。现
在是缓坡下降（听说过股市里的尖底圆顶么？）。一旦加速下降，就是主跌浪开始了，
学名叫中国金融危机。当然这会是美国的叫法，中国会把它叫做第二次金融危机（暗示
是美国引起的）。你可以很快验证看看这名词。如果你真好学的话，下面给你贴一篇教
学文章。其中的几个名人，Bill Gross，是太平洋基金的创始人之一，也是中投2011年
雇的朱长虹的老板的老板。George Soros，大名鼎鼎，就不多说了。Michael Diekmann
，世界最大的保险公司的老板。这篇文章里有很多信息，都和现在的金融市场和即将发
生的金融危机相关。
Fall of the Bond King: How Gross Lost Empire as Pimco Cracked
By Mary Childs - Dec 3, 2014
Bill Gross, the 70-year-old king of bonds, rushed through the offices of his
$2 trillion empire on a ... 阅读全帖 |
|
t***h
发帖数: 5601 | 34 http://www.ctbto.org/the-treaty/developments-after-1996/2013-dp
Media questions and answers on radionuclide detection
Vienna, 23 April 2013
1. How come the detection was made so late (when you said on 12 March that
it was improbable)?
A: The main detection was made on 8 and 9 April, a smaller one from 12 to 14
April. Detection of radioactive noble gas more than 7 weeks after an event
is indeed unusual, we did not expect this and it did not happen in 2009. We
do not know what has happened at the ... 阅读全帖 |
|
g**1
发帖数: 10330 | 35 Facts force Washington Post to backtrack on report that Russia hacked US
power grid
https://www.rt.com/usa/372448-washingtonpost-retracts-russian-hackers/
Editor’s Note: An earlier version of this story incorrectly said that
Russian hackers had penetrated the U.S. electric grid. Authorities say there
is no indication of that so far. The computer at Burlington Electric that
was hacked was not attached to the grid. |
|
L*****d
发帖数: 5093 | 36 http://newyork.cbslocal.com/2017/03/23/jewish-community-center-arrest/
Israeli Police Arrest Jewish Teen In Bomb Threats Against US Jewish
Community Centers
NEW YORK (CBSNewYork/AP) — Israeli police arrested a 19-year-old Israeli
Jewish man as the primary suspect in a string of bomb threats targeting
Jewish community centers and other institutions in the U.S., marking a
potential breakthrough in a case that stoked fears across America.
Police spokesman Micky Rosenfeld described the suspect as a ... 阅读全帖 |
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b*********3
发帖数: 1709 | 37 【 以下文字转载自 USANews 讨论区 】
发信人: beijingren3 (), 信区: USANews
标 题: 黑客对床铺炸叙利亚发出警告了
发信站: BBS 未名空间站 (Sat Apr 8 14:37:51 2017, 美东)
https:[email protected]/* *//dont-forget-your-base-867d304a94b1
Don’t Forget Your Base
Respectfully, what the fuck are you doing? TheShadowBrokers voted for you.
TheShadowBrokers supports you. TheShadowBrokers is losing faith in you. Mr.
Trump helping theshadowbrokers, helping you. Is appearing you are abandoning
“your base”, “the movement”, and the peoples who gettin... 阅读全帖 |
|
t***h
发帖数: 5601 | 38 https://wikileaks.org/plusd/cables/10PANAMA87_a.html
Date: 2010 February 23, 19:07 (Tuesday)
Canonical ID: 10PANAMA87_a
Original Classification: CONFIDENTIAL
Current Classification: CONFIDENTIAL
Type: TE - Telegram (cable)
From: Panama Panama City
To: Belize Belmopan | Central Intelligence Agency | China Beijing | Colombia
Bogota | Costa Rica San Jose | Defense Intelligence Agency | Ecuador Quito
| El Salvador San Salvador | Honduras Tegucigalpa | National Security
Council | Nicaragua Managua | ... 阅读全帖 |
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W*****B
发帖数: 4796 | 39 马特达蒙之前力挺哈维，绝对不信性侵故事。现在哈维倒了，他又改口说听说过性侵，
但是是从好基友本阿弗莱克听说。这些戏子有一点可信度吗。
Matt Damon now admits he knew about at least one accusation against Harvey
Weinstein
Matt Damon is backtracking on his claims he knew nothing of Harvey Weinstein
's alleged behavior of sexual harassment and assault.
The actor previously said he "never saw" the alleged behavior and it
's "not true" that "we all knew."
Now Damon is admitting he was aware that Weinstein allegedly sexually
harassed Gwyneth Pal... 阅读全帖 |
|
W*****B
发帖数: 4796 | 40
Poland and Israel in Tense Talks Over Law Likened to Holocaust Denial
JERUSALEM — Polish and Israeli officials met on Thursday to address the
diplomatic rift that erupted over a new Polish law that makes it a crime to
blame Poland for the Holocaust, a measure that Israeli officials have
likened to Holocaust denial.
The law, adopted last month over the furious objections of Israel and
scholars from around the world, makes it a crime... 阅读全帖 |
|
|
s*x
发帖数: 8041 | 42 Avatar
John Springer • 14 hours ago
Just read how Russia built second pipeline to China and no longer using
dollars , but petro yuans and rubles. We can no longer simply use threat of
sanctions and tariffs. We can negotiate but must treat our peers, even those
who see the world differently, as participants or we will fail.
6
•Reply•
Avatar
Orange Juice John Springer • an hour ago
Who will buy our debt if we upset China? Trump arranged for record deficits
and he's trying... 阅读全帖 |
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s*x
发帖数: 8041 | 43 Lyin' Donnie will trade away access to the South China Sea since he was told
he can't build a golf course there anyway.
Likethumb_up1
Replyreply
Linklink
Reportflag
trumprising
6 minutes ago
(Edited)
MAGA!! Damn if the Trump train isn't gaining speed!
Who would have thought one man could slay all the working mans demons ?
I honesty believe there will be a Mount Trumpmore type monument when its all
said and done in 2025.
Likethumb_up
Replyreply
Linklink
Reportflag
Show More Replies
talkytina
7 mi... 阅读全帖 |
|
a******1
发帖数: 1031 | 44
ok I backtrack 宁可冒着活埋的风险 也不能让公知抓着不放
不把人都搬出来 能确认都死亡了么？
事发5小时就停止救援 说生命探测仪找不到生命迹象 结果之后还能找到生还者
埋人的可能性是很大的
当然你也可以抬杠 说我没证据 是瞎猜 叙述不准确 是造谣
是没证据 都给埋了么 |
|
发帖数: 1 | 45 在跟一个实际经济比自己大三倍的国家搞贸易战。
其实经济总量就是每个人的衣食住行，中国除了汽油烧得少点，其他完胜美国。体量太
大了。有的人算中国经济是一百，美国是二百。但是改开前中国十亿人被算成3或5。所
谓的经济学家就是弱智小虫在算大象。
既然是war比的就是人口，粮食，钢铁。
所以说特朗铺输了一点儿不丢人。以后会被评为无知的猛士。
Tesla, BMW Bypass Trump’s Trade War and Score a Win for China
By Angus Whitley and Enda Curran
July 13, 2018, 5:34 AM EDT
Beijing says Tesla plant an ‘achievement’ of its opening-up
Germany, China strike deal that’s sweet for German automakers
Tesla's China Timeline Isn't Feasible, Auto Analyst Albertine Says
Less than a week int... 阅读全帖 |
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b*****d
发帖数: 61690 | 46 Alibaba founder Jack Ma on Wednesday backtracked on his plan to create 1
million jobs in the United States, two days after President Trump slapped
tariffs on about $200 billion worth of Chinese imports.
"The promise was made on the premise of friendly US-China partnership and
rational trade relations," Ma told Chinese news organization Xinhua,
according to CNBC. "That premise no longer exists today, so our promise
cannot be fulfilled." |
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发帖数: 1 | 47 我老说我放弃接盘奶茶了
：Alibaba founder Jack Ma on Wednesday backtracked on his plan to create 1
：million jobs in the United States, two days after President Trump slapped |
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m*****t
发帖数: 16663 | 48 翻字典都读不懂英语新闻，这里是我引用的CNN原话：
British investigators are still trying to determine the identities and
nationalities of the eight women and 31 men in the container, which was on
the back of a truck. Each person was carrying a bag of personal belongings
and many had mobile phones, which are being downloaded and forensically
analyzed, police said in a statement.
Authorities in the UK initially said that they thought the dead people may
have been Chinese citizens, but later backtracked as the possibility... 阅读全帖 |
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m*****t
发帖数: 16663 | 49 翻字典都读不懂英语新闻，这里是我引用的CNN原话：
British investigators are still trying to determine the identities and
nationalities of the eight women and 31 men in the container, which was on
the back of a truck. Each person was carrying a bag of personal belongings
and many had mobile phones, which are being downloaded and forensically
analyzed, police said in a statement.
Authorities in the UK initially said that they thought the dead people may
have been Chinese citizens, but later backtracked as the possibility... 阅读全帖 |
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发帖数: 1 | 50 蝇文都看不明白的，到Montreal对Québécois彻底抓瞎，被鹅毛mafia卖给爱斯基摩部落
https://www.mitbbs.com/article/Military/54916763_0.html
Authorities in the UK initially said that they thought the dead people may
have been Chinese citizens, but later backtracked as the possibility emerged
that at least one of the passengers was Vietnamese. It's not clear what
informed the initial assessment.。
这里没有任何确认有至少一名越南死者的意思，只是说有至少一名越南死者的可能性，
而且也不是被官方确认的，你们理解错了这句话，这话是说，官方最初说他们认为死者
是中国公民，but后面是CNN的看法，而不是前面官方的看法， |
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