无论我使用什么作为输入，输出都是零

您正在制作大小为 5 的vector：

const int NEW_WEIGHT = 5;
vector<float> inputWeights(NEW_WEIGHT);
// == 0, 0, 0, 0, 0

然后，在输入循环中，您将新值添加到末尾：

inputWeights.push_back (42);
// == 0, 0, 0, 0, 0, 42

然后你输出前五个元素，它们总是零。

您需要选择一件事或另一件事：要么在程序开始时设置矢量的大小，要么在有输入的情况下用push_back增长矢量。两者都是有效的选项。

您可以通过采用现代C++(如 C++11 及更高版本)习惯用法来清理代码并解决问题。您不再需要用for(int i = 0; i < something; i++)填充代码。有一种更简单的方法。

// 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);
}

无论哪种情况，您都可以使用另一个基于范围的for来播放填充的矢量：

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

如果您在输入期间调整向量的大小，您还需要从输入循环中删除cout << inputWeights[i] << endl;行 - 正如所写的那样，您将读取尚不存在的元素，并且可能会得到数组索引越界异常。

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);

将其更改为仅

vector<float> inputWeights;

并在代码中删除这一行或将其注释掉

cout << inputWeights[i]<< endl; 

这是您从程序要求中寻找的内容。

#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以下两行代码：

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

这与执行此操作相同：

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

然后，您可以使用NEW_WEIGHT遍历容器时更容易使用inputWeights.size()，从而循环访问多达 5 个元素。

编辑 - 精简版

#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;
}