Question

这是我正在处理的问题：

提示用户输入五个数字，即五个人的权重。将数字存储在双打矢量中。在一行上输出向量的数字，每个数字后跟一个空格。
还可以通过对矢量元素求和来输出总重量。
还输出向量元素的平均值。

还输出最大矢量元素。到目前为止，这是我的代码

#include <iostream>
#include <vector>
using namespace std;

int main() {
   const int NEW_WEIGHT = 5;
   vector<float> inputWeights(NEW_WEIGHT);
   int i = 0;
   float sumWeight = 0.0;
   float AverageWeight = 1.0;
   int maxWeight = 0;
   int temp = 0;

   for (i = 0; i < NEW_WEIGHT; i++){
      cout << "Enter weight "<< i+1<< ": ";
      cout << inputWeights[i]<< endl; 
      cin>> temp;
      inputWeights.push_back (temp);

   }


   cout << "\nYou entered: ";

   for (i =0; i < NEW_WEIGHT- 1; i++) {

      cout << inputWeights.at(i)<< " ";
   }
   cout<< inputWeights.at(inputWeights.size() - 1) << endl;

   for (i =0; i < NEW_WEIGHT; i++){

       sumWeight += inputWeights.at(i); 

   }
   cout <<"Total weight: "<< sumWeight<< endl;

   AverageWeight = sumWeight / inputWeights.size();

   cout <<"Average weight: "<< AverageWeight<< endl;

   maxWeight= inputWeights.at(0);
   for (i =0; i < NEW_WEIGHT- 1; i++){
       if (inputWeights.at(i) > maxWeight){
          maxWeight = inputWeights.at(i);
       }
    }

    cout<< "Max weight: "<< maxWeight << endl;

    return 0;
}

当我运行此代码时，无论我使用什么输入（对于cin＆gt;＆gt;（...）），我都将零作为输出，我不知道为什么。我可以帮忙吗。

更新通过摆脱 cout＆lt;＆lt;＆lt;＆lt;＆lt;＆lt;＆lt;＆lt; inputWeights [1] - ;＆LT; ENDL;
并在程序开头调整向量inputWeights; 。但输出仍然不是它们应该是的。相反，只有前2个输入值使其成为输出。有什么理由吗？谢谢

更新这是正确或正确的代码。希望将来有人帮助。

#include <iostream>
#include <vector>

using namespace std;

int main() {
   const int NEW_WEIGHT = 5;
   vector <float> inputWeights;
   int i = 0;
   float sumWeight = 0.0;
   float AverageWeight = 1.0;
   float maxWeight = 0.0;
   float temp = 0.0;

   for (i = 0; i < NEW_WEIGHT; i++){
      cout << "Enter weight "<< i+1<< ": "<< endl;
      cin>> temp;
      inputWeights.push_back (temp);

      }


      cout << "\nYou entered: ";

   for (i =0; i < NEW_WEIGHT- 1; i++){

      cout << inputWeights.at(i)<< " ";
   }
      cout<< inputWeights.at(inputWeights.size() - 1) << endl;

    for (i =0; i < NEW_WEIGHT; i++){

       sumWeight += inputWeights.at(i); 

      }
   cout <<"Total weight: "<< sumWeight<< endl;

       AverageWeight = sumWeight / inputWeights.size();

   cout <<"Average weight: "<< AverageWeight<< endl;

      maxWeight= inputWeights.at(0);
    for (i =0; i < NEW_WEIGHT- 1; i++){
       if (inputWeights.at(i) > maxWeight){
          maxWeight = inputWeights.at(i);
          }
    }

   cout<< "Max weight: "<< maxWeight << endl;

   return 0;
}

Answer 1

您正在制作尺寸为5的vector：

const int NEW_WEIGHT = 5;
vector<float> inputWeights(NEW_WEIGHT);

// == 0, 0, 0, 0, 0

然后，在您的输入循环中，您需要在结尾添加新值：

inputWeights.push_back (42);

// == 0, 0, 0, 0, 0, 42

然后你输出前五个始终为零的元素。

您需要选择一件事或另一件事：在程序开始时设置矢量的大小，或者只要输入push_back就增长矢量。两者都是有效的选择。

您可以通过采用现代C ++（如C ++ 11及更高版本）习惯来清理代码并修复问题。您不需要再使用for(int i = 0; i < something; i++)填写代码。这是一种更简单的方法。

// Size fixed in advance:
vector<float> weights(NUM_WEIGHTS);

for (auto& weight : weights) { // note it's `auto&`
  cout << "\nEnter next weight: ";
  cin >> weight; // if it was plain `auto` you'd overwrite a copy of an element of `weight`
}

// Size decided by input:
vector<float> weights; // starts empty this time

cout << "Enter weights. Enter negative value to stop." << endl;
float in;
while (cin >> in) {
  if(in < 0) {
    break;
  }
  weights.push_back(in);
}

在任何一种情况下，您都可以使用其他基于范围的for来播放填充的矢量：

cout << "You entered: ";
for (const auto& weight : weights) {
  cout << weight << " ";
}

如果您在输入过程中调整了矢量大小，您还需要从输入循环中删除cout << inputWeights[i] << endl;行 - 正如您所写的那样，您正在阅读尚不存在的元素，并且可能会得到一个数组索引超出范围的异常。

Answer 2

当您创建定义输入权重时，您将使用默认值将5个项目放入其中。

vector<float> inputWeights(NEW_WEIGHT);

将其更改为

vector<float> inputWeights;

在代码中删除此行或将其注释掉

cout << inputWeights[i]<< endl;

Answer 3

这是您正在寻找的程序要求。

#include <vector>
#include <iostream>

int main() {
    std::vector<double> weights;

    double currentWeight = 0.0;
    const unsigned numberOfWeights = 5;
    std::cout << "Enter " << numberOfWeights << " weights" << std::endl;
    unsigned i = 0;
    for ( ; i < numberOfWeights; ++i ) {
        std::cin >> currentWeight;
        weights.push_back( currentWeight );
    }

    std::cout << "These are the weights that you entered: " << std::endl;
    for ( i = 0; i < weights.size(); ++i ) {
        std::cout << weights[i] << " ";
    }
    std::cout << std::endl;

    double totalWeight = 0.0;
    std::cout << "The total of all weights is: ";
    for ( i = 0; i < weights.size(); ++i ) {
        totalWeight += weights[i];
    }
    std::cout << totalWeight << std::endl;

    std::cout << "The average of all the weights is: " << (totalWeight / numberOfWeights) << std::endl;

    std::cout << "The max weight is: ";
    double max = weights[0];
    for ( i = 0; i < weights.size(); ++i ) {
        if ( weights[i] > max ) {
            max = weights[i];
        }
    }
    std::cout << max << std::endl;

    return 0;
}

将所有0视为输出的问题的罪魁祸首来自这两行代码：

const int NEW_WEIGHT = 5;
vector<float> inputWeights(NEW_WEIGHT);

与执行此操作相同：

vector<float> inputWeights{ 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };

然后使用NEW_WEIGHT循环最多5个元素，这样在遍历容器时更容易使用inputWeights.size()。

编辑 - 简明版

#include <vector>
#include <iostream>

int main() {
    std::vector<double> weights;

    double currentWeight           = 0.0;
    const unsigned numberOfWeights = 5;
    unsigned i = 0;

    std::cout << "Enter " << numberOfWeights << " weights" << std::endl;
    for ( ; i < numberOfWeights; ++i ) {
        std::cin >> currentWeight;
        weights.push_back( currentWeight );
    }

    double totalWeight = 0.0;
    double max         = weights[0];
    std::cout << "These are the weights that you entered: " << std::endl;
    for ( i = 0; i < weights.size(); ++i ) {
        std::cout << weights[i] << " ";   // Print Each Weight
        totalWeight += weights[i];        // Sum The Weights

        // Look For Max Weight
        if ( weights[i] > max ) {
            max = weights[i];
        }
    }
    std::cout << std::endl;

    std::cout << "The total of all weights is: " << totalWeight << std::endl;
    std::cout << "The average of all the weights is: " << (totalWeight / numberOfWeights) << std::endl;
    std::cout << "The max weight is: " << max << std::endl;

    return 0;
}

无论我用作输入，输出都是零

3 个答案: