c++ - 在 C++ 中打印一个数组

Question

我正在尝试做一些 C++ 作业，但我似乎遇到了问题。我需要让用户输入 8 个数字，然后将 8 个数字存储在一个数组中。然后，如果其中一个数字大于 21，则输出该数字。代码在下面，有点草率。是的，这里是第一年 C++ 学习者 :p

#include <iostream>
  using namespace std;

  int main() {
  const int NUM_ELEMENTS = 8; // Number of elements
  int userVals[NUM_ELEMENTS]; // User numbers
  int i = 0;                  // Loop index
  int sumVal = 0;             // For computing sum
  int prntSel = 0;            // For printing greater than 21

  // Prompt user to populate array
  cout << "Enter " << NUM_ELEMENTS << " integer values..." << endl;


  for (i = 0; i < NUM_ELEMENTS; ++i) {
     cin >> userVals[i];
  }

  for (int i = NUM_ELEMENTS - 1; i > 21; i--)
     cout << "Value: " << sumVal << endl;

  // Determine sum
  sumVal = 0;

  for (i = 0; i < NUM_ELEMENTS; ++i) {
     sumVal = sumVal + userVals[i];
  }

  cout << "Sum: " << sumVal << endl;

  return 0;
}

Answer 1

不要重新发明轮子，use standard algorithms :

std::copy_if(std::begin(userVals), std::end(userVals),
             std::ostream_iterator<int>(std::cout, "\n"),
             [] (auto x) { return x > 21; });

我也改进了你程序的其余部分:

#include <algorithm>
#include <iostream>
#include <iterator>
#include <numeric>
#include <vector>

auto constexpr count = 8;

int main() {
    std::vector<int> numbers(count);

    std::cout << "Enter " << count << " integer values...\n";
    std::copy_n(std::istream_iterator<int>(std::cin), numbers.size(), numbers.begin());

    std::copy_if(numbers.begin(), numbers.end(),
                 std::ostream_iterator<int>(std::cout, "\n"),
                 [] (auto x) { return x > 21; });

    auto sum = std::accumulate(numbers.begin(), numbers.end(), 0);
    std::cout << "Sum: " << sum << '\n';

    return 0;
}

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