好的我正在尝试这个程序，我必须让用户输入学生姓名，然后输入他们的考试成绩。我正在尝试设置它，所以我将拥有一系列名称和一系列成绩。我无法将名称添加到数组中。我试图在for循环中调用cin.getline（）并将其分配给数组中的每个下标。然而，它失败了。有人能指出我正确的方向吗？
#include<iostream>
#include<iomanip>
#include<string>
using namespace std;
//Function prototypes
void sort(double*, int);
double average(double*, int);
void drop(double*, int);
int main()
{
char ch;
char name[30];
int numTestScores;
string *studentNames;
double *testScorePtr;
double testAverage;
//Get the number of test scores.
cout << "\nHow many test scores will you enter? ";
cin >> numTestScores;
//Validate the input.
/*while (numTestScores < 0)
{
cout << "The number cannot be negative.\n";
cout << "Enter another number: ";
cin >> numTestScores;
}*/
// Allocate an array to hold the test scores
studentNames = new string[numTestScores];
testScorePtr = new double[numTestScores];
//Fill the array with test scores.
for(int i = 0; i < numTestScores; i++)
{
cout << "Enter name and test score for test # "
<< (i+1) << " : "<< endl;
cin.getline(name,30);
studentNames[i] = name;
cout << studentNames[i] <<endl; //I tried to use this to see if the names were going into the array
cin.get();
}
//Get a test score.
//cout << "Enter test score "
//<< (i + 1) << ": ";
//cin >> testScorePtr[i];
//Validate the input.
/*while (numTestScores < 0)
{
cout << "Negative scores are not allowed.\n";
cout << "Enter another score for this test: ";
cin >> testScorePtr[i];*/
// Sort the test scores.
sort(testScorePtr, numTestScores);
//Display the resulting data.
cout << "\nThe test scores in ascending "
<< "order, and their average, are:\n\n";
cout << "Score" <<endl;
cout << "----" <<endl;
for (int j = 0; j < numTestScores; j++)
{
cout << "\n" << fixed << setprecision(2)
<< setw(6) << testScorePtr[j];
}
//Drop The Lowest Grade
drop(testScorePtr, numTestScores);
// Get the average of the test scores.
testAverage = average(testScorePtr, numTestScores);
cout << "\n\nAverage score: " << setprecision(2) << fixed << testAverage <<endl <<endl;
// Free the dynamically-allocated memory.
delete [] testScorePtr;
testScorePtr = 0;
return 0;
}
//****************************************
//Function sort
//This function performs a selection sort
//on the array pointed to by the score
//parameter into ascending order. The size
//parameter holds the number of elements.
//*****************************************
void sort(double* score, int size)
{
int startScan, minIndex;
double minValue;
for (startScan = 0; startScan < (size - 1); startScan++)
{
minIndex = startScan;
minValue = score[startScan];
for(int index = startScan + 1; index < size; index++)
{
if (score[index] < minValue)
{
minValue = score[index];
minIndex = index;
}
}
score[minIndex] = score[startScan];
score[startScan] = minValue;
}
}
void drop(double* score, int size)
{
score[0] = 0;
}
//*************************************************
//Function average
//This function calculates and returns the
//average of the values stored in the array
//passed into the scores parameter. The
//parameter numScors holds the number of elements in the array
double average(double* score, int numScores)
{
double total = 0; //Accumulator
numScores--;
//Calculate the total of the scores.
for (int k = 0; k <= numScores ; k++)
{
total += score[k];
}
//Return the average score.
return (total/numScores);
}
答案 0 :(得分：2)
您没有考虑换行符。
这一行：
cin >> numTestScores;
从输入中读取一个数字，但不是换行符。因此，如果您输入8＆lt; enter＆gt;你读了8但是没有从输入中读取换行符 所以你第一次进入循环并执行此操作：
cin.getline(name,30);
这将读取您在8之后键入的新行字符（而不是其他内容）。
其他几个陷阱...
1）忘记阅读并扔掉换行符。
cin >> numTestScores;
解决方案：
// 1: Read the line into a string then read the value from the string.
std::string testScoresString;
std::getline(std::cin, testScoresString);
std::stringstream testScoreStream(testScoreString);
testScoreStream >> numTestScores
// 2: Use boost::lexical cast on the string stream:
std::string testScoresString;
std::getline(std::cin, testScoresString);
testScoreStream = boost::lexical_cast<int>(testScoreString);
// 3: Read number then ignore input to the new line character
cin >> numTestScores;
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n')
2：不要在C ++代码中使用new / delete
你可以使用新的动态对象，但记住要删除它们很难。您应该使用智能指针或容器来控制动态对象的生命周期。
studentNames = new string[numTestScores];
testScorePtr = new double[numTestScores];
在这种情况下，最好使用std :: vector。
std::vector<std::string> studentNames(numTestScores);
std::vector<double> testScorePtr(numTestScores);
3：不要将固定大小的数组用于用户输入：
cin.getline(name,30);
您只是要求用户崩溃您的程序。输入一个真正的长名称 使用将行读入std :: string的版本。字符串将根据需要进行扩展。
std::getline(std::cin, studentNames[i]);
4：你不需要在这里使用endl。如果希望缓冲区刷新，请使用endl。我一直用它，所以它实际上很好。只是想确保你知道它冲刷了缓冲区。
cout << studentNames[i] <<endl;
4：不确定这是为了什么。阅读并丢掉下一行的第一个字符!!!!!!
cin.get();
5：注意这很好用。作为＆gt;＆gt;运算符在搜索下一个分数时忽略换行符。
//Get a test score.
//cout << "Enter test score "
//<< (i + 1) << ": ";
//cin >> testScorePtr[i];
6：就像我上面预测的那样，你忘了删除其中一个阵列。只需使用矢量。你使用new / delete的任何地方你都在编写类似C的代码。好的C ++代码几乎没有删除它（除非你正在编写智能指针/容器）。
delete [] testScorePtr;
7：你知道有std::sort method。
void sort(double* score, int size)
8：你可以靠近std::accumulate
double average(double* score, int numScores)