通过代码实例解析c++ vector常用方法

1. c++ vector 每个元素加上一个特定值 (c++ vector add a constant value for each element)

https://stackoverflow.com/questions/4461446/stl-way-to-add-a-constant-value-to-a-stdvector

vector<int> x = {0, 30, 80, 100, 120, 150, 190, 220, 250};
//transform可以将函数应用到序列的元素上,bind2nd通过绑定其中一个参数把二元函数转换成一元函数
transform(x.begin(), x.end(), x.begin(), bind2nd(plus<int>(), 1));
//显示x的值
copy(x.begin(), x.end(), ostream_iterator<int>(cout, " "));

结果： x = {1 31 81 101 121 151 191 221 251}

2. c++判断vector中是否存在某个元素（c++ judge whether an element exists in the vector）

https://www.techiedelight.com/check-vector-contains-given-element-cpp/

#include <iostream>
#include <vector>
#include <algorithm>

int main()
{
  std::vector<int> v = { 4, 7, 5, 2, 6, 9 };
  int key = 6;

  if (std::count(v.begin(), v.end(), key))
    std::cout << "Element found";
  else
    std::cout << "Element not found";

  return 0;
}

结果显示：Element found

3. c++ vector<int> 生成指定个数的顺序列表 （c++ generate a sequential vector<int> of special numbers）

https://stackoverflow.com/questions/17694579/use-stdfill-to-populate-vector-with-increasing-numbers

 std::vector<int> seq(10);
 // 定义在 numeric 头文件中的 iota() 函数模板会用连续的 T 类型值填充序列
 std::iota(seq.begin(), seq.end(), 0);

结果： seq = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

4. c++ 一条语句打印vector信息（c++ print out vector by one statement）.

https://stackoverflow.com/questions/10750057/how-to-print-out-the-contents-of-a-vector

 vector<int> x = {1, 2, 3, 4};
 //istream_iterator用于从输入流中读取连续的元素
 copy(x.begin(), x.end(), ostream_iterator<int>(cout, " "));

结果显示： 1 2 3 4

5. c++ 得到vector<int>中元素的最大值和最小值以及最大值和最小值的索引位置 （c++ get the maximum and minimum values of the elements in vector<int> and the index positions ）

https://riptutorial.com/cplusplus/example/11151/find-max-and-min-element-and-respective-index-in-a-vector

vector<int> row_y = { 502, 263, 684, 324, 979 };

// 最大值索引和最大值
int row_y_max_index = max_element(row_y.begin(), row_y.end()) - row_y.begin();
cout << "row_y_max_index = " << row_y_max_index << endl;
int row_y_max_value = *max_element(row_y.begin(), row_y.end());
cout << "row_y_max_value = " << row_y_max_value << endl;

// 最小值索引和最小值
int row_y_min_index = min_element(row_y.begin(), row_y.end()) - row_y.begin();
cout << "row_y_min_index = " << row_y_min_index << endl;
int row_y_min_value = *min_element(row_y.begin(), row_y.end());
cout << "row_y_min_value = " << row_y_min_value << endl;

结果返回：

row_y_max_index = 4
row_y_max_value = 979
row_y_min_index = 1
row_y_min_value = 263

6. c++ vector 相加两个vector (c++ append a vector to vector)

https://stackoverflow.com/questions/2551775/appending-a-vector-to-a-vector

 vector<int> x = {0, 30, 80, 100, 120, 150, 190, 220, 250};
 vector<int> y = {100};
 y.insert(y.end(), x.begin(), x.end());

结果：y = {100, 0, 30, 80, 100, 120, 150, 190, 220, 250}

7. c++ 复制vector（c++ copy vector）

https://www.geeksforgeeks.org/ways-copy-vector-c/

vector<int> x = {0, 30, 80, 100, 120, 150, 190, 220, 250};
 vector<int> y;
 y.assign(x.begin(), x.end());

结果：y = {0, 30, 80, 100, 120, 150, 190, 220, 250}

8. c++ vector 根据给定索引删除元素（c++ vector delete element based on a given index）

https://iq.opengenus.org/ways-to-remove-elements-from-vector-cpp/

若想要删除第2个索引值和到第5个索引值，则可以使用下以语句：

 vector<int> x = {0, 30, 80, 150, 120, 150, 30, 220, 80};
 //remove(x.begin(), x.end(), 80);
 x.erase(x.begin() + 2, x.begin() + 5 + 1);

结果： x = {0, 30, 30, 220, 80}

9. c++ 删除vector所有指定元素（c++ delete all specified elements in the vector）

https://www.techiedelight.com/erase-elements-vector-cpp/

 vector<int> x = {0, 30, 150, 30, 220, 80};
 //vector中的remove的作用是将等于value的元素放到vector的尾部，但并不减少vector的size
 //vector中erase的作用是删除掉某个位置position或一段区域（begin, end)中的元素，减少其size
 x.erase(remove(x.begin(), x.end(), 30), x.end());

结果： x = {0 150 220 80}

10. c++ 统计 vector 某个元素出现的次数 (C++ count the number of occurrences of an element in vector)

https://www.geeksforgeeks.org/std-count-cpp-stl/

 vector<int> x = { 0, 3, 5, 6, 3, 2, 3 };
 int n = count(x.begin(), x.end(), 3);

结果：n = 3

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