1 #include<iostream> 2 #include<algorithm> 3 #include<vector> 4 #include<string> 5 #include<fstream> 6 using namespace std; 7 8 void elimDups(vector<string> &words) 9 { 10 sort(words.begin(), words.end()); 11 auto unique_end = unique(words.begin(), words.end()); 12 words.erase(unique_end, words.end()); 13 } 14 15 void display(vector<string> &words) 16 { 17 for (auto c : words) 18 cout << c << " "; 19 cout << endl; 20 } 21 22 int main() 23 { 24 ifstream in("test.txt"); 25 if (!in) 26 { 27 cout << "打开文件失败" << endl; 28 exit(1); 29 } 30 31 vector<string> words; 32 string str; 33 while (in >> str) 34 words.push_back(str); 35 elimDups(words); 36 display(words); 37 return 0; 38 }
输出结果：
定制操作
示例代码：
1 #include<iostream> 2 #include<algorithm> 3 #include<vector> 4 #include<string> 5 #include<fstream> 6 using namespace std; 7 8 void elimDups(vector<string> &words) 9 { 10 sort(words.begin(), words.end()); 11 auto unique_end = unique(words.begin(), words.end()); 12 words.erase(unique_end, words.end()); 13 } 14 15 void biggies(vector<string> &words, vector<string>::size_type sz) 16 { 17 elimDups(words); //将单词按字典排序，删除重复单词 18 stable_sort(words.begin(), words.end(), [](const string &a, const string &b) { return a.size() < b.size(); }); 19 auto wc = find_if(words.begin(), words.end(), [sz](const string &a) { return a.size() >= sz; }); 20 auto count = words.end() - wc; 21 for_each(wc, words.end(), [](const string &s) { cout << s << " "; }); 22 cout << endl; 23 } 24 25 int main() 26 { 27 ifstream in("test.txt"); 28 if (!in) 29 { 30 cout << "打开文件失败" << endl; 31 exit(1); 32 } 33 34 vector<string> words; 35 string str; 36 while (in >> str) 37 words.push_back(str); 38 auto sz = 5; 39 biggies(words, sz); 40 return 0; 41 }
输出结果：
再探迭代器
3. 反向迭代器
1 #include<iostream> 2 #include<vector> 3 #include<iterator> 4 using namespace std; 5 6 int main() 7 { 8 vector<int> vec = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; 9 for (auto r_iter = vec.crbegin(); r_iter != vec.crend(); ++r_iter) 10 cout << *r_iter << " "; 11 cout << endl; 12 return 0; 13 }
输出结果：
1 #include <iostream> 2 #include <deque> 3 #include <algorithm> 4 #include <iterator> 5 using namespace std; 6 7 void print(int elem) 8 { 9 cout << elem << ' '; 10 } 11 12 int main() 13 { 14 deque<int> coll; 15 for (int i = 1; i <= 9; ++i) 16 coll.push_back(i); 17 18 deque<int>::iterator pos1; 19 pos1 = find(coll.begin(), coll.end(), 2); 20 21 deque<int>::iterator pos2; 22 pos2 = find(coll.begin(), coll.end(), 7); 23 for_each(pos1, pos2, print); 24 cout << endl; 25 26 deque<int>::reverse_iterator rpos1(pos1); 27 deque<int>::reverse_iterator rpos2(pos2); 28 for_each(rpos2, rpos1, print); 29 cout << endl; 30 return 0; 31 }
输出结果：
【分析】
代码首先在一个deque中插入1到9，然后查找元素值为2和7的位置，分别赋值给迭代器pos1和pos2，然后输出，由于STL中的操作总是左开右闭的区间，即[2,7)，所以输出2 3 4 5 6，7不会输出。
接下来将迭代器转换成逆向迭代器，再次输出，对于反向迭代器，由于是反向，所以按逻辑来说它是左开右闭的（这里我尝试了rpos2为iterator.end(),rpos1为iterator.begin(),此时输出全部），即(7,2]（事实上还是左闭右开，只不过此时的左和iterator顺序一样）。所以输出6 5 4 3 2，下面的图片解释的很清楚。
