被 leetcode 上的靠前的答案震惊了

V2EX = way to explore

V2EX 是一个关于分享和探索的地方

已注册用户请登录

这是一个创建于 2548 天前的主题，其中的信息可能已经有所发展或是发生改变。

https://leetcode.com/problems/count-and-say/description/

好奇点开了排名第一的答案。。。。很多人也许见怪不怪了吧

高中搞 NOIP 的时候还想过，如果有题目不会做，我就直接把题目给的输入输出给直接输出，当然并没有去做。

class Solution: def countAndSay(self, n): """ :type n: int :rtype: str """ D = {1: '1', 2: '11', 3: '21', 4: '1211', 5: '111221', 6: '312211', 7: '13112221', 8: '1113213211', 9: '31131211131221', 10: '13211311123113112211', 11: '11131221133112132113212221', 12: '3113112221232112111312211312113211', 13: '1321132132111213122112311311222113111221131221', 14: '11131221131211131231121113112221121321132132211331222113112211', 15: '311311222113111231131112132112311321322112111312211312111322212311322113212221', 16: '132113213221133112132113311211131221121321131211132221123113112221131112311332111213211322211312113211', 17: '11131221131211132221232112111312212321123113112221121113122113111231133221121321132132211331121321231231121113122113322113111221131221', 18: '31131122211311123113321112131221123113112211121312211213211321322112311311222113311213212322211211131221131211132221232112111312111213111213211231131122212322211331222113112211', 19: '1321132132211331121321231231121113112221121321132122311211131122211211131221131211132221121321132132212321121113121112133221123113112221131112311332111213122112311311123112111331121113122112132113213211121332212311322113212221', 20: '11131221131211132221232112111312111213111213211231132132211211131221131211221321123113213221123113112221131112311332211211131221131211132211121312211231131112311211232221121321132132211331121321231231121113112221121321133112132112312321123113112221121113122113121113123112112322111213211322211312113211', 21: '311311222113111231133211121312211231131112311211133112111312211213211312111322211231131122211311122122111312211213211312111322211213211321322113311213212322211231131122211311123113223112111311222112132113311213211221121332211211131221131211132221232112111312111213111213211231132132211211131221232112111312211213111213122112132113213221123113112221131112311311121321122112132231121113122113322113111221131221', 22: '132113213221133112132123123112111311222112132113311213211231232112311311222112111312211311123113322112132113213221133122112231131122211211131221131112311332211211131221131211132221232112111312111213322112132113213221133112132113221321123113213221121113122123211211131221222112112322211231131122211311123113321112131221123113111231121113311211131221121321131211132221123113112211121312211231131122211211133112111311222112111312211312111322211213211321322113311213211331121113122122211211132213211231131122212322211331222113112211', 23: 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26: 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27: 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28: 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29: 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30: 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return D[n]

第 1 条附言 2018-11-14 16:56:54 +08:00

大家已经不是见怪不怪了，而是习以为常了。

个人觉得在 LeetCode 这个平台，更多的是研究解题思路，写出优雅的解法。

正文中的例子，虽然能通过测试，但不具有泛化性，可以说在生产过程中基本毫无用处，应该算是违背平台的初衷了吧。

leetcode

答案

字典

15 条回复 2018-11-14 16:43:17 +08:00

huntzhan

2018-11-13 22:46:38 +08:00

leetcode 打表还行

24bit

2018-11-13 22:48:33 +08:00

习惯就好

midasplus

2018-11-13 22:49:39 +08:00

搞过 noip 应该知道骗分和打表呀(

vegito2002

2018-11-13 23:40:24 +08:00

leetcode contest 比赛的时候这种人多了去了, 见一个举报一个

xxx749

2018-11-13 23:44:12 +08:00 via Android

这题目什么意思，没看懂

nililnellaf

2018-11-13 23:44:50 +08:00

noip 骗分不奇怪啊手算也只能算个小数据

mmnsghgn

2018-11-13 23:47:53 +08:00

https://leetcode.com/problems/stone-game/description/

`return true`

yuikns

2018-11-13 23:54:21 +08:00 via iPhone

@xxx749 每一步都是上一步的描述

1
一个 1，即 11
二个 1，即 21
一个 2，一个 1，即 1211
... 以此类推

Xs0ul

2018-11-14 00:02:08 +08:00

@zhengjian #7 我也看过这个，必胜策略就是比奇偶两列那个多，然后只取多的那个

xxx749

2018-11-14 00:48:14 +08:00 via Android

正则的性能这么差的吗？ JS 才 beats 15.11

yuikns

2018-11-14 01:18:31 +08:00

刚发现这道题我是做过的。
两年前是这么写的 (0ms)：

void i2v(int i, vector<int> & r) {
int offset = r.size() - 1;
while (i > 0) {
r.push_back(i % 10);
i /= 10;
}
for (int j = offset; j < (r.size() - offset) / 2; j++) {
int t = r[j];
r[j] = r[r.size() - 1 - j - offset];
r[r.size() - 1 - j - offset] = t;
}
}

vector<int> gen(vector<int> &c, int n) {
if (n > 0) {
vector<int> r;
int vv = c[0];
int vc = 0;
for (int i = 0; i < c.size(); i++) {
if (c[i] == vv) {
vc++;
} else {
i2v(vc,r);
r.push_back(vv);
vc = 1;
vv = c[i];
}
}
if (vc > 0) {
i2v(vc,r);
r.push_back(vv);
}
return gen(r, n - 1);
} else {
return c;
}
}

string countAndSay(int n) {
vector<int> c;
c.push_back(1);
vector<int> r = gen(c, n - 1);
char str[r.size() + 1];
str[r.size()] = '\0';
for (int i = 0; i < r.size(); i++) {
//s += (char)(r[i] + '0');
str[i] = r[i] + '0';
}
return string(str);
}

现在是这么写的 (4ms):

string countAndSay(int n) {
if(n <= 1) return "1";
string prev = countAndSay(n-1);
string buff = "";
char ci = '\0';
int cc = 0;
for(auto c : prev) {
if(c != ci) {
if(ci != '\0') {
buff += to_string(cc);
buff += ci;
}
ci = c;
cc = 1;
} else {
cc ++;
}
}
if (cc > 0) {
buff += to_string(cc);
buff += ci;
}
return buff;
}

越来越水了...

elikoi17

2018-11-14 04:00:16 +08:00 via Android

打表蒙点是正常操作吧。。。

echoZero

2018-11-14 09:51:05 +08:00

打表算是个正常的操作有时候
case 优先打表是可以过得

nyaruko

2018-11-14 14:13:26 +08:00

noip 确实有这么骗分的。中学参加过这类比赛的应该都熟悉。。

但是 leetcode 也这么玩。有点不好吧。毕竟是锻炼算法的地方

xmt328

2018-11-14 16:43:17 +08:00

打表也算是一个骗分的经典操作了