在prior question的基础上，我有一个单词＆amp;他们的计数存储在map<string, int>中。我想反过来，以便所有具有相同计数的单词组合在一起。我的解决方案是使用vector<vector<string> >。第一个向量的索引是count＆amp;第二个向量是单词的集合。
在阅读上一个问题的答案之后，这里我一直在努力工作：
vector<vector<string> > sorted_words;
for (map<string, int>::const_iterator it = counters.begin();
it != counters.end(); ++it) {
cout << "word:" << it->first
<< " count:" << it-> second
<< " vector size: " << sorted_words.size()
<< endl;
if (sorted_words.size() - 1 > it->second &&
sorted_words[ it->second ].size() > 0) {
cout << "Adding " << it->first << endl;
sorted_words[ it->second ].push_back(it->first);
} else {
cout << "Creating " << it->first << endl;
vector<string> v;
v.push_back(it->first);
sorted_words.resize( it->second + 1 );
sorted_words[it->second] = v;
}
}
这导致在if语句的第一次循环中出现段错误。
我要做的是查看外部矢量的大小是否使我的当前值为inbounds＆amp;如果是这样，如果我已经创建了嵌套向量。 （我需要这样做，因为地图可以按任何顺序返回。例如，第一个元素可以是＆lt;“foo”，3＆gt ;.）
如果我以基本的非C ++方式进行，请随时指出。
答案 0 :(得分：4)
快速猜测：sorted_words.size()是一些无符号类型（即size_t）所以sorted_words.size() - 1是无符号的，即使它应该是-1（最初）因此你总是通过第一个条件if条件的后半部分评估并崩溃。
答案 1 :(得分：3)
对于太空，您最好使用std::map<int, std::vector<string>>。以下相当简单的代码（可以通过降低所有单词和剥离标点符号来改进）演示：
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <map>
using namespace std;
int main(int argc, char *argv[])
{
if (argc < 2)
return EXIT_FAILURE;
// map of strings to counts.
std::map<string, int> strs;
ifstream inf(argv[1]);
string str;
while (inf >> str)
++strs[str];
// map of counts to strings, smallest to largest.
std::map<int, std::vector<string>> vals;
for (auto it : strs)
vals[ it.second ].push_back(it.first);
// report counts for each
for (auto it : vals)
{
cout << "Count: " << it.first << ": ";
std::copy(it.second.begin(), it.second.end(),
ostream_iterator<string>(cout, " "));
cout << endl;
}
}
示例输入
我从W.莎士比亚的“你喜欢它”中选择了一个独白，它有一些有趣的属性，你会在稍后看到：
All the world's a stage,
And all the men and women merely players:
They have their exits and their entrances;
And one man in his time plays many parts,
His acts being seven ages. At first, the infant,
Mewling and puking in the nurse's arms.
And then the whining school-boy, with his satchel
And shining morning face, creeping like snail
Unwillingly to school. And then the lover,
Sighing like furnace, with a woeful ballad
Made to his mistress' eyebrow. Then a soldier,
Full of strange oaths and bearded like the pard,
Jealous in honour, sudden and quick in quarrel,
Seeking the bubble reputation
Even in the cannon's mouth. And then the justice,
In fair round belly with good capon lined,
With eyes severe and beard of formal cut,
Full of wise saws and modern instances;
And so he plays his part. The sixth age shifts
Into the lean and slipper'd pantaloon,
With spectacles on nose and pouch on side,
His youthful hose, well saved, a world too wide
For his shrunk shank; and his big manly voice,
Turning again toward childish treble, pipes
And whistles in his sound. Last scene of all,
That ends this strange eventful history,
Is second childishness and mere oblivion,
Sans teeth, sans eyes, sans taste, sans everything.
示例输出
Count: 1: All At Even For In Into Is Jealous Last Made Mewling Sans Seeking Sighing That The Then They Turning Unwillingly acts again age ages. all all, arms. ballad beard bearded being belly big bubble cannon's capon childish childishness creeping cut, ends entrances; eventful everything. exits eyebrow. eyes eyes, face, fair first, formal furnace, good have he history, honour, hose, infant, instances; justice, lean lined, lover, man manly many men mere merely mistress' modern morning mouth. nose nurse's oaths oblivion, one pantaloon, pard, part. parts, pipes players: pouch puking quarrel, quick reputation round satchel saved, saws scene school-boy, school. second seven severe shank; shifts shining shrunk side, sixth slipper'd snail so soldier, sound. spectacles stage, sudden taste, teeth, this time too toward treble, voice, well whining whistles wide wise woeful women world world's youthful
Count: 2: Full His With on plays strange their to
Count: 3: like sans then with
Count: 4: a of
Count: 6: in
Count: 7: his
Count: 8: And
Count: 11: and the
有趣的是独白中的独特单词串的数量很大。几乎就像他那样计划。但是，在考虑大写和删除标点符号时，这些数字明显不同。值得庆幸的是，这样做也是微不足道的，只改变了第一个while循环：
while (inf >> str)
{
string alpha;
for_each(str.begin(), str.end(),
[](char& c){c=tolower(static_cast<unsigned char>(c));});
copy_if(str.begin(), str.end(), back_inserter(alpha),
[](const char& c){return isalpha(static_cast<unsigned char>(c));});
++strs[alpha];
}
这给了我们以下结果：
Count: 1: acts again age ages arms at ballad beard bearded being belly big bubble cannons capon childish childishness creeping cut ends entrances even eventful everything exits eyebrow face fair first for formal furnace good have he history honour hose infant instances into is jealous justice last lean lined lover made man manly many men mere merely mewling mistress modern morning mouth nose nurses oaths oblivion one pantaloon pard part parts pipes players pouch puking quarrel quick reputation round satchel saved saws scene school schoolboy second seeking seven severe shank shifts shining shrunk side sighing sixth slipperd snail so soldier sound spectacles stage sudden taste teeth that they this time too toward treble turning unwillingly voice well whining whistles wide wise woeful women world worlds youthful
Count: 2: eyes full on plays strange their to
Count: 3: all like
Count: 4: a of sans then
Count: 5: with
Count: 7: in
Count: 9: his
Count: 12: the
Count: 19: and
仍然，相当令人印象深刻，比利。
由于第一个地图排序的性质，您可以获得额外的奖励，您可以按字母顺序按字母顺序获取生成的单词列表。 Woot奖金功能。
答案 2 :(得分：0)
如果您要反转map<K, V>，请使用map<V, vector<K>>。如果您不关心该点的实际计数，您可以通过从中间地图移动来有效地构建vector<vector<V>>。例如：
vector<vector<string>> invert(const map<string, int>& input) {
map<int, vector<string>> inverse;
for (const auto& pair : input)
inverse[pair.second].push_back(pair.first);
vector<vector<string>> result;
for (auto& pair : inverse)
result.push_back(move(pair.second));
return result;
}
答案 3 :(得分：0)
您可以使用已有的地图（vector<vector<string>>）而不是拥有map<int, vector>或倒置的地图，例如map<string, int>，而只需创建vector<vector<int>>来收集所有具有相同计数的单词的指数。这将为您节省大量空间。此外，当您修改之前的map<string, int>时，您需要更新vector<vector<int>>中的索引，这将比其他两种方法更快。