std::vector 如何对数组进行assign 和 push_back操作。

1） assign

  char arr[] = { 1,2,3 };
  std::vector<char> buffer;
  buffer.clear();
  buffer.insert(buffer.begin(), std::begin(arr), std::end(arr));
  assert(buffer.size() == 3);
  assert(buffer[0] == 1);
  assert(buffer[1] == 2);
  assert(buffer[2] == 3);

    或者

  char arr[] = { 101, 1,2,3 };
  std::vector<char> buffer(100, 100);
  buffer.assign(std::begin(arr), std::end(arr));
  assert(buffer.size() == 4);
  assert(buffer[0] == 101);
  assert(buffer[1] == 1);
  assert(buffer[2] == 2);
  assert(buffer[3] == 3);

或者

  char arr[] = { 101, 1,2,3 };
  std::vector<char> buffer(arr, arr + sizeof(arr)/sizeof(arr[0]));
  assert(buffer.size() == 4);
  assert(buffer[0] == 101);
  assert(buffer[1] == 1);
  assert(buffer[2] == 2);
  assert(buffer[3] == 3);

    如果只赋值数组的一部分：

  char arr[] = { 101, 1,2,3 };
  std::vector<char> buffer(arr, arr + 2);
 
  assert(buffer.size() == 2);
  assert(buffer[0] == 101);
  assert(buffer[1] == 1);

    或者

  char arr[] = { 101, 1,2,3 };
  std::vector<char> buffer(std::begin(arr), std::begin(arr) + 2);
 
  assert(buffer.size() == 2);
  assert(buffer[0] == 101);
  assert(buffer[1] == 1);

2) push_back

  char arr[] = { 1,2,3 };
  std::vector<char> buffer(1, 100);
  buffer.insert(buffer.cend(), std::cbegin(arr), std::cend(arr));
  assert(buffer.size() == 4);
  assert(buffer[0] == 100);
  assert(buffer[1] == 1);
  assert(buffer[2] == 2);
  assert(buffer[3] == 3);

    如果只赋值数组的一部分：

  char arr[] = { 1,2,3 };
  std::vector<char> buffer(1, 100);
  buffer.insert(buffer.cend(), std::cbegin(arr), std::cbegin(arr) + 1);
  assert(buffer.size() == 2);
  assert(buffer[0] == 100);
  assert(buffer[1] == 1);