C++ Vector fundamental
主要內容包括： 引入標頭檔案，如何建立並初始化，訪問容量，增查刪改；
1. 包含標頭檔案
#include <vector>
#include <iostream>
2. 建立 vector
vector<int> v;
vector<char> v1;
vector<string> v2;
3. 初始化一維 vector
初始化後不進行賦值，直接訪問會報錯；
3.1 vector v
vector <int> v;
v.resize(5); // 使用 5 個 0 來初始化
for (int i=0; i < v.size(); i++){
cout << v[i] << " ";
}
cout << endl;
vector<int> v1;
v1.resize(5, 1); // 使用 5 個 1 來初始化
for (int i=0; i < v1.size(); i++){
cout << v1[i] << ' ';
}
cout << endl;
3.2 vector v=
vector<int> v = {1, 2, 3, 4, 5};
v.resize(3); // 丟棄元素 4 和 5
// 1， 2， 3
for(int i=0; i<v.size(); i++){
cout << v[i] << ' ';
}
cout << endl;
vector<int> v1 = {1, 2, 3, 4, 5};
v1.resize(7); // 填充0
// 1， 2， 3， 4， 5， 0， 0
for (int i=0; i < v1.size(); i++){
cout << v1[i] << ' ';
}
cout << endl;
3.3 copy vector
vector<int> testVector = {1, 2, 3, 4, 5};
vector<int> v(testVector);
// 1, 2, 3, 4, 5
for(int i=0; i<v.size(); i++){
cout << v[i] << " ";
}
cout << endl;
vector<int> testVector = {1, 2, 3, 4, 5};
vector<int> v = testVector;
for (int i=0; i<v.size(); i++){
cout << v[i] << " ";
}
cout << endl;
3.4 pointer init vector
int arr[5] = {1, 2, 3, 4, 5};
vector<int> v = {1, 2, 3, 4};
// 1, 2, 3
vector<int> v1(arr, arr+3);
for (int i =0; i < v1.size(); i++){
cout << v1[i] << " ";
}
cout << endl;
// 2, 3
vector<int> v2(v.begin()+1, v.end()-1);
for(int i=0; i<v2.size(); i++){
cout << v2[i] << " ";
}
cout << endl;
4. 初始化二維 vector
初始化後不進行賦值，直接訪問會報錯
4.1 vector<vector > v;
vector< vector<int>>v;
v.resize(5);
for (int i=0; i<5; i++){
v.resize(5);
}
// all output si 0
for(int i=0; i<v.size();i++){
for (int j=0; j<v[i].size();j++){
cout << v[i][j] << " ";
}
cout << endl;
}
cout << endl;
4.2 vector <vector> v(n, testVctor)
vector <int> testVector(4, 1);
vector < vector<int> > v(4, testVector);
// 4*4 output is 1
for(int i=0; i<v.size(); i++){
for(int j=0; j<v[i].size();j++){
cout << v[i][j] << " ";
}
cout << endl;
}
cout << endl;
4.3 pointer init vector
// vector 的指標
vector <int> v1 = {1, 2, 3, 4};
vector< vector<int> > v2(4, v1);
/* 1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
*/
vector< vector<int> > v3(v2.begin(), v2.end());
for(int i=0; i<v3.size(); i++){
for(int j=0; j<v3[i].size(); j++){
cout << v3[i][j] << " ";
}
cout << endl;
}
cout << endl;
// 普通陣列的指標
int arr[4][4] = {
{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}, {13, 14, 15, 16}
};
vector<vector <int>> v;
for(int i=0; i<4; i++){
vector<int> row(arr[i], arr[i]+4);
v.push_back(row);
}
for(int i=0; i<v.size(); i++){
for(int j=0; j<v[i].size(); j++){
cout << v[i][j] << ' ';
}
cout << endl;
}
cout << endl;
5. 直接訪問 vector 中的元素
vector<int> v = {100, 200, 300, 400};
cout << v[0] << endl;
cout << v[1] << endl;
cout << v[2] << endl;
cout << v[3] << endl;
6. 獲取 vector 大小
vecotr <int> v = {100, 200, 300, 400, 500};
cout << v.size() << endl;
cout << v.capacity() << endl;
7. 向 vector 新增元素
vector<int> v = {100, 200, 300};
// 向末尾新增元素
v.push_back(1);
v.push_back(2);
v.push_back(3);
for(int i=0; i<v.size(); i++){
cout << v[i] << " ";
}
cout << endl;
8. 向 vector 插入元素
vector <int> v1 = {100, 200, 300, 400, 500, 600};
vector <int>::iterator it;
it = v1.begin();
v1.insert(it, 111);
// out: 111, 100, 200, 300, 400, 500, 600
for(int i=0; i<v1.size(); i++){
cout << v1[i] << " ";
}
cout << endl;
it = v1.begin() + 2;
v1.insert(it, 222);
// out: 111, 100, 222, 200, 300, 400, 500, 600
for(int i=0; i<v1.size(); i++){
cout << v1[i] << " ";
}
cout << endl;
it = v1.end();
v1.insert(it, 999);
for(int i=0; i<v1.size(); i++){
cout << v1[i] << " ";
}
cout << endl;
9. 刪除 vector 中的元素：pop_back
vector<int> v = {100, 200, 300, 400. 500};
v.pop_back(); // 刪除末尾元素
v.pop_back();
cout << v.size() << endl;
for(int i=0; i<v.size(); i++){
cout << v[i] << " ";
}
cout << endl;
10. 刪除 vector 指定位置的元素: erase
vector<int> v = {1, 2, 3, 4, 5, 6};
vector<int>::iterator it;
it = v.begin();
v.erase(it);
// out: 2, 3, 4, 5, 6
for(int i=0; i<v.size();i++){
cout << v[i] << " ";
}
cout << endl;
it = v.begin() + 2;
v.erase(it);
//out: 2, 3, 5, 6
for(int i=0; i<v.size();i++){
cout << v[i] << " ";
}
cout << endl;
11. 刪除 vector 制定數值的元素：remove
#include <algorithm>
vector<int> v = {100, 200, 300, 400, 500, 600};
v.erase(remove(v.begin(), v.end(), 500), v.end());
v.erase(remove(v.begin(), v.end(), 300), v.end());
// out: 100, 200, 400, 600
for(int i=0; i < v.size(); i++){
cout << v[i] << " ";
}
cout << endl;
#include <algorithm>
vector <int> v = {100, 200, 300, 400, 500, 600};
v.erase(remove(v.begin(), v.end(), 555), v.end()); // 找不到值，不執行任何操作
v.erase(remove(v.begin(), v.end(), 333), v.end());
for(int i=0; i<v.size(); i++){
cout << v[i] << " ";
}
cout << endl;
12. 修改 vector 中的元素
vector<int> v = {100, 200, 300, 400, 500, 600};
v[0] = 111;
v[1] = 222;
for(int i=0; i< v.size(); i++){
cout << v[i] << " ";
}
cout << endl;
13. 查詢 vector 中的元素
#include <algorithm>
vector<int> v = {100, 200, 300, 400, 500};
vector<int>::iterator it = find(v.begin(), v.end(), 500);
if (it != v.end()){
cout << "index: " << distance(v.begin(), it) << endl;
}
else{
cout << "not found" << endl;
}
#include <algorithm>
vector<int> v = {100, 200, 300, 400, 500, 600};
bool found = false;
int valueToFind = 300;
for(vector<int>::iterator it=v.begin(); it!=v.end(); ++it){
if (*it == valueToFind){
cout << "index: " << distance(v.begin(), it) << endl;
found = true;
break;
}
}
if(!found){
cout << "not found" << endl;
}
14. 清空 vector 中的元素：clear
vector<int> v = {100, 200, 300, 400, 500, 600};
cout << v.size() << endl; //out: 6
v.clear();
cout << v.size() << endl; //out: 0
15. 索引遍歷 vector 元素
vector <int> v = {100, 200, 300, 400, 500};
for(int i=0; i<v.size(); i++){
cout << v[i] << " ";
}
cout << endl;
16. 迭代器遍歷 vector 元素
vector <int> v = {100, 200, 300, 400, 500};
for(vector<int>::iterator it = v.begin(); it != v.end(); it++){
cout << *it << " ";
}
cout << endl;
17. 使用 foreach 迴圈遍歷
vector <int> v = {100, 200, 300, 400, 500};
// auto it 是自動型別推斷，直接取得元素值
for(auto it:v){
cout << it << " ";
}
cout << endl;