HW2 Publish

docs/vector.cpp

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