C++ code Summary --- 2015.11.8

C++ code summary


map<int, PersonClassifier>::iterator it与 map<int, PersonClassifier> it的区别与联系

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C++
并行程序的执行：

int
coreNum = omp_get_num_procs();

#pragma
omp parallel for
num_threads(coreNum) default(none)
\

private(po_num,
it, queryLabel) \

shared(al_random_select_num,
satisfy_size, satisfy_classifier_label, not_selected, random_index)

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对输入的句子，统计每一个单词出现的次数：

int
main() {

map<string,
size_t>
word_count;

string
word;

while
(cin >>
word) {

++word_count[word];

}

for
(constauto
&w : word_count)

cout
<<
w.first <<"occurs"<<
w.second

<<
((w.second > 1) ? "times"
: "time")
<<
endl;

system("pause");

}

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统计输入中每一个单词出现的次数（排除常见单词，如：”the”,
”a”, ”an”等等）

#include<iostream>

#include<string>

#include<map>

#include<set>

usingnamespace
std;

int
main() {

map<string,
size_t>
word_count;

set<string>
exclude = {"the",
"a",
"an"};

string
word;

while
(cin >>
word)

if
(exclude.find(word) ==
exclude.end())

++word_count[word];

for
(constauto
&w : word_count)

cout
<<
w.first <<"
occurs "<<
w.second <<"
times "<<
endl;

system("pause");

}

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忽略大小写和标点，如：”example,”
“example.” “Example”应该递增相同计数器。

　　　分为３步骤：

　　　１．先将所有的大写字母改为小写；

　　　２．将所有的标点符号都删去；

　　　３．将转换好的字符串返回．

#include<iostream>
#include<fstream>
#include<map>
#include<string>
#include<algorithm>

using namespace std;

string &trans(string &s)
{
for (int p=0; p<s.size(); p++){
if (s[p] >= 'A' && s[p] <= 'Z')
s[p] -= ('A'-'a');
else if (s[p] == ',' || s[p] == '.')
s.erase(p,1);
}

return s;
}

int main(int argc, char *argv[])
{
ifstream in(argv[1]);
if (!in){
cout<<"failed to open file !"<<endl;
exit(1);
}

map<string, size_t> word_count;
string word;
while(in>>word)
++word_count(trans(word));

for (const auto &w:word_count)
cout<<　w.first　<<　" occurs "　<<　w.second　<<　" times "　<<endl;

return 0;
}

　　　

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对关联容器进行值初始化：

map<string, size_t> word_count;

set<string> exclude = {“the”, ”but”, “and”};

map<string, string> authers = { {“wang”, “xiao”},
{“wang”, ”kui”}, {“wang”, ”jianjun”} };

#include<iostream>

#include<string>

#include<map>

#include<set>

#include<vector>

usingnamespace
std;

int
main() {

vector<int>
ivec;

for
(vector<int>::size_type
i = 0; i != 20; ++i) {

ivec.push_back(i);

ivec.push_back(i);

}

set<int>
iset(ivec.cbegin(), ivec.end());

multiset<int>
miset(ivec.cbegin(), ivec.cend());

cout
<<
ivec.size() <<
endl;

cout
<<
iset.size() <<
endl;

cout
<<
miset.size() <<
endl;

system("pause");

}

pair类型：

一个pair保存两个数据成员，pair是一个用来生成特定类型的模板。

pair<string, string> anon;

pair<string, size_t> word_count;

pair<string, vector<int>> line;

pair<string, string> auther {“wangxiao”, “wangkui”};

pair类型的数据成员是public的，两个成员分别为
first 和
second。

9. ----

#include<iostream>
#include<string>
#include<map>

using namespace std;

int main() {
map<string, size_t> word_count;
string word;
while (cin >> word) {
++word_count[word];
}

for (const auto &w : word_count)
cout << w.first << "occurs" << w.second
<< ((w.second > 1) ? "times" : "time") << endl;

system("pause");
}