C++ code Summary --- 2015.11.8

C++ code summary

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

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

     return s;
 }

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

     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 ;
 }

　　　

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1. 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");

}

1. 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");
}