147 lines
5.3 KiB
C++
147 lines
5.3 KiB
C++
#include <iostream>
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#include <vector>
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struct student {
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int number; // 學號
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int score; // 成績
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};
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int main(){
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std::vector<student> students;
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students.push_back(student{1, 100});
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students.push_back(student{2, 90});
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students.push_back(student{3, 80});
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students.push_back(student{4, 70});
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students.push_back(student{5, 60});
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// ----------- 掃過 vector 中每一個值 範例 -----------
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// 會改變原本的值
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std::cout << "method 1:" << std::endl;
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std::vector<student> s1 = students; //從 students 複製一個一模一樣的vector
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for (int i = 0; i < s1.size(); i++) {
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s1[i].number = 1;
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std::cout << '(' << s1[i].number << ',' << s1[i].score << ") ";
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}
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std::cout << std::endl;
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std::cout << "original vector:" << std::endl;
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for (auto s: s1) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl << std::endl;
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// 不會改變原本的值
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std::cout << "method 2:" << std::endl;
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std::vector<student> s2 = students;
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for (auto s: s2) { // auto也可以寫成 student
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s.number = 2;
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl;
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std::cout << "original vector:" << std::endl;
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for (auto s: s2) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl << std::endl;
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// 會改變原本的值
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std::cout << "method 3:" << std::endl;
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std::vector<student> s3 = students;
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for (auto& s: s3) { // auto也可以寫成 student
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s.number = 3;
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl;
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std::cout << "original vector:" << std::endl;
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for (auto& s: s3) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl << std::endl;
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// 結論：
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// 只要在資料型態後面加上 & (reference) 就可以改變原本的資料
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// auto 可以自動偵測資料型態
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// ----------- 取得 vector 最前面的值 範例 -----------
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std::cout << "number: " << students.front().number << std::endl;
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std::cout << "score: " << students.front().score << std::endl;
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// ----------- 取得 vector 最後面的值 範例 -----------
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std::cout << "number: " << students.back().number << std::endl;
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std::cout << "score: " << students.back().score << std::endl;
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// ----------- 取得 vector 最前面的指標 範例 -----------
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std::cout << "number: " << (*students.begin()).number << std::endl;
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std::cout << "score: " << (*students.begin()).score << std::endl;
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// ----------- 取得 vector 最後面的指標 範例 -----------
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std::cout << "number: " << (*(students.end()-1)).number << std::endl;
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std::cout << "score: " << (*(students.end()-1)).score << std::endl;
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std::cout << std::endl;
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// ----------- 刪除 vector 最前面的值 範例 -----------
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std::vector<student> s4 = students;
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std::cout << "original vector:" << std::endl;
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for (auto& s: s4) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl;
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s4.erase(s4.begin());
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std::cout << "after erase vector:" << std::endl;
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for (auto& s: s4) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl << std::endl;
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// ----------- 刪除 vector 第i個的值 範例 -----------
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std::vector<student> s5 = students;
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std::cout << "original vector:" << std::endl;
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for (auto& s: s5) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl << std::endl;
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s5.erase(s5.begin() + 1);
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std::cout << "after erase vector:" << std::endl;
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for (auto& s: s5) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl << std::endl;
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// ----------- 刪除 vector 最後面的值 範例 -----------
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std::vector<student> s6 = students;
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std::cout << "original vector:" << std::endl;
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for (auto& s: s6) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl << std::endl;
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s6.erase(s6.end());
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std::cout << "after erase vector:" << std::endl;
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for (auto& s: s6) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl << std::endl;
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// ----------- 清空 vector 範例 -----------
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std::vector<student> s7 = students;
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std::cout << "original vector:" << std::endl;
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for (auto& s: s7) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl << std::endl;
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s7.clear();
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std::cout << "after clear vector:" << std::endl;
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for (auto& s: s7) { // auto也可以寫成 student
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std::cout << '(' << s.number << ',' << s.score << ") ";
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}
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std::cout << std::endl << std::endl;
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return 0;
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} |