C++ Primer-迭代器和第三章习题-优快云博客

迭代器（iterator）

P96:使用迭代器将字符串中的每个元素变成大写：

 1 #include <iostream>
 2 #include <vector>
 3 #include <string>
 4 #include <typeinfo>
 5 using namespace std;
 6 int main()
 7 {
 8     string s("some string");
 9     if (s.begin() != s.end()) {
10         for (auto it = s.begin(); it != s.end() /*&& !isspace(*it)*/; ++it) {
11             *it = toupper(*it);
12         }
13     }
14     cout << s << " ";
15     cout << endl;
16     system("pause");
17     return 0;
18 }

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迭代器类型：

#include <iostream>
#include <vector>
#include <string>
#include <typeinfo>
using namespace std;
int main()
{
    vector<int>::iterator it;//it能读写vector<int>的元素
    string::iterator it2;//it2能读写string对象中的元素
    vector<int>::const_iterator it3;//it3能读vector<int>的元素，不能写元素
    string::iterator it4;//it4能读string对象中的元素，不能写元素
}

P98:依次输出text的每一行直至遇到第一个空白行为止

 1 #include <iostream>
 2 #include <vector>
 3 #include <string>
 4 #include <typeinfo>
 5 using namespace std;
 6 int main()
 7 {
 8     vector<string> text{ "some string" };
 9     for (auto it = text.cbegin(); it != text.cend() && !it->empty(); ++it) {
10         cout << *it << endl;
11     }
12     system("pause");
13     return 0;
14 }

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3.22

 1 #include <iostream>
 2 #include <vector>
 3 #include <string>
 4 #include <typeinfo>
 5 using namespace std;
 6 int main()
 7 {
 8     vector<string> text{ "some string" };
 9     for (string::size_type i = 0; i < text.size(); ++i) {
10         for (string::size_type j = 0; j < text[i].size(); ++j) {
11             text[i][j] = toupper(text[i][j]);
12         }
13     }
14     for (auto it = text.cbegin(); it != text.cend() && !it->empty(); ++it) {
15         cout << *it << endl;
16     }
17     system("pause");
18     return 0;
19 }

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由用户输入：

 1 #include <iostream>
 2 #include <vector>
 3 #include <string>
 4 #include <typeinfo>
 5 using namespace std;
 6 int main()
 7 {
 8     vector<string> text;
 9     string temp;
10     getline(cin, temp);
11     text.push_back(temp);
12     for (string::size_type i = 0; i < text.size(); ++i) {
13         for (string::size_type j = 0; j < text[i].size(); ++j) {
14             text[i][j] = toupper(text[i][j]);
15         }
16     }
17     for (auto it = text.cbegin(); it != text.cend() && !it->empty(); ++it) {
18         cout << *it << " ";
19         cout << endl;
20     }
21     system("pause");
22     return 0;
23 }

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3.23

 1 #include <vector>
 2 #include <string>
 3 using namespace std;
 4 int main()
 5 {
 6     vector<int> v(10,1);
 7     for (string::size_type i = 0; i < v.size(); ++i) {
 8         v[i] *= 2;
 9     }
10     for (auto it = v.cbegin(); it != v.cend(); ++it) {
11         cout << *it << endl;
12     }
13     system("pause");
14     return 0;
15 }

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P100:使用迭代器计算：

 1 #include <iostream>
 2 #include <vector>
 3 #include <string>
 4 using namespace std;
 5 int main()
 6 {
 7     vector<int> text{ 1,2,3,4,5,6,7,8};
 8     auto beg = text.begin(), end = text.end();
 9     auto mid = text.begin() + (end - beg) / 2;
10     int sought = 3;
11     while (mid != end && *mid != sought) {
12         if (sought < *mid) {
13             end = mid;
14         }
15         else {
16             beg = mid + 1;
17         }
18         mid = beg + (end - beg) / 2;
19     }
20     cout << *mid << endl;
21     system("pause");
22     return 0;
23 
24 }

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利用for循环和push_back添加100个数：

 1 #include <iostream>
 2 #include <vector>
 3 #include <string>
 4 using namespace std;
 5 int main()
 6 {
 7     vector<int> text;
 8     for (string::size_type i = 0; i < 100; ++i) {
 9         text.push_back(i);
10     }
11     /*for (string::size_type i = 0; i < text.size(); ++i) {
12         cout << text[i];
13     }*/
14     auto beg = text.begin(), end = text.end();
15     auto mid = text.begin() + (end - beg) / 2;
16     int sought = 55;
17     while (mid != end && *mid != sought) {
18         if (sought < *mid) {
19             end = mid;
20         }
21         else {
22             beg = mid + 1;
23         }
24         mid = beg + (end - beg) / 2;
25     }
26     cout << *mid << " ";
27     cout << endl;
28     system("pause");
29     return 0;
30 
31 }

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用户输入要查找的数：

 1 #include <iostream>
 2 #include <vector>
 3 #include <string>
 4 using namespace std;
 5 int main()
 6 {
 7     vector<int> text;
 8     for (string::size_type i = 0; i < 1000; ++i) {
 9         text.push_back(i);
10     }
11     auto beg = text.begin(), end = text.end();
12     auto mid = text.begin() + (end - beg) / 2;
13     int sought;
14     cout << "输入要查找的数：" << endl;
15     cin >> sought;
16     while (mid != end && sought != *mid) {
17         if (sought < *mid) {
18             end = mid;
19         }
20         else {
21             beg = mid + 1;
22         }
23         mid = beg + (end - beg) / 2;
24     }
25     cout << *mid << " ";
26     cout << endl;
27     system("pause");
28     return 0;
29 }

View Code

3.24所编写的程序不完美，限定vector对象的元素个数为偶数，否则报错：

 1 #include <iostream>
 2 #include <vector>
 3 #include <string>
 4 using namespace std;
 5 int main()
 6 {
 7     vector<int> text;
 8     for (string::size_type i = 0; i < 1002; ++i) {
 9         text.push_back(i);
10     }
11     /*
12     for (string::size_type i = 0; i < text.size(); ++i) {
13         cout << text[i] << endl;
14     }
15     */
16     for (auto beg = text.begin(), end = text.end(); beg != end; ++beg) {
17         --end;
18         cout << *beg + *end << endl;
19     }
20     system("pause");
21     return 0;
22 }

View Code

3.25

 1 #include <iostream>
 2 #include <vector>
 3 #include <string>
 4 using namespace std;
 5 int main()
 6 {
 7     vector<unsigned> scores(11, 0);
 8     unsigned grade;
 9     while (cin >> grade) {
10         ++scores[grade / 10];
11     }
12     for (auto beg = scores.begin(), end = scores.end(); beg != end; ++beg) {
13         cout << *beg << endl;
14     }
15     system("pause");
16     return 0;
17 }