双维数组读取错误
Double dimension array read error
我有一个双维std ::字符串阵列，我需要将其作为函数参数 sortstring 进行传递，但是当变量 student时，我会遇到一个运行时错误首先阅读。" 0"是通过COUT输出，而不是" 1"。我对我错的地方有任何想法吗？
这是我的代码：
#include <iostream>
#include <string>
void sortString(std::string **student, std::string **output, int size)
{
std::string names[5];
std::cout << "0" << std::endl;
for (int i = 0 ; i < size ; i++)
names[i] = student[i][0];
std::cout << "1" << std::endl;
}
int main()
{
std::string student1 [ ] = {"Joe Lime", "15", "2019"};
std::string student2 [ ] = {"Bob Green", "3", "2020"};
std::string student3 [ ] = {"SallyAnne Green" , "1", "2017"};
std::string student4 [ ] = {"Annie Blue", "10", "2020"};
std::string student5 [ ] = {"Jose Lemon", "25", "2016"};
int const size = 5;
std::string student [5][3] = {student1, student2, student3, student4, student5};
std::string sortedByName[5][3];
sortString((std::string**)student, (std::string**)sortedByName, size);
return 0;
}
** -------------编辑-------------- **
我想做与一维数组相同的事情，所以我不明白为什么它不适用于二维数组
，例如，这有效：
#include <iostream>
int test(int *a)
{
std::cout << a[0] << std::endl;
}
int main()
{
int a[] = {1,2,3,4,5,6,7};
test(a);
}
int test(int *a)
{
std::cout << a[0] << std::endl;
}
您对数组，指针和字符串有很大的混乱。作为@quentin和 @molbdnilo指出了您的指出，您正在从bidemensional阵列的std ::字符串到指向字符串指针的指针进行C风格的转换，而数组都不是指针，也不是指针。
我的猜测是，您想根据他们的名字对所有学生进行分类，同时将其余的学生信息与相应的学生保持联系。
一些建议：
- 只要您可以使用std ::数组。 ，请勿使用C风格数组。
- 要在代码中定义常数，创建一个常数变量，例如，在您想更改该常数值时，这可能涉及代码不同部分的多个更改，因为它可以写在多个位置。
- 您不需要在示例中使用指针。在这种情况下，它们没有意义。
您要实现的示例使用std :: sort函数：
#include <string>
#include <array>
#include <iostream>
#include <algorithm>
const unsigned NUMBER_OF_STUDENTS = 5;
const unsigned NUMBER_OF_STUDENT_DATA_FIELDS = 3;
using studentType = std::array<std::string, NUMBER_OF_STUDENT_DATA_FIELDS>;
int main()
{
std::array<std::string, NUMBER_OF_STUDENT_DATA_FIELDS> student1 = {"Joe Lime", "15", "2019"};
std::array<std::string, NUMBER_OF_STUDENT_DATA_FIELDS> student2 = {"Bob Green", "3", "2020"};
std::array<std::string, NUMBER_OF_STUDENT_DATA_FIELDS> student3 = {"SallyAnne Green" , "1", "2017"};
std::array<std::string, NUMBER_OF_STUDENT_DATA_FIELDS> student4 = {"Annie Blue", "10", "2020"};
std::array<std::string, NUMBER_OF_STUDENT_DATA_FIELDS> student5 = {"Jose Lemon", "25", "2016"};
std::array<studentType, NUMBER_OF_STUDENTS> students = {student1, student2, student3, student4, student5};
std::sort(students.begin(), students.end(), [](const studentType& student1, const studentType& student2) {
// first string in the array is the name
const std::string& nameStudent1 = student1.front();
const std::string& nameStudent2 = student2.front();
// we return if the name of student 1 is lexicographically smaller than the name of student 2
return nameStudent1 < nameStudent2;
});
// Let's print the students to see we have order everything correctly
for (const auto& student: students) // for each student
{
for (const auto& studentData : student) // for each field in the student string
{
std::cout << studentData << " ";
}
std::cout << "n"; // jump to the next line
}
}
Annie Blue 10 2020
鲍勃·格林3 2020
Joe Lime 15 2019
Jose Lemon 25 2016
Sallyanne Green 1 2017
我稍微修复了您的代码，并使其正常工作：
#include <iostream>
#include <string>
void sortString(std::string student[][3], std::string output[][3], int size)
{
std::string names[5];
std::cout << "0" << std::endl;
for (int i = 0; i < size; i++)
{
names[i] = student[i][0];
std::cout << names[i] << "n";
}
std::cout << "1" << std::endl;
}
int main()
{
int const size = 5;
std::string students[5][3] =
{
{ "Joe Lime", "15", "2019" },
{ "Bob Green", "3", "2020" },
{ "SallyAnne Green", "1", "2017" },
{ "Annie Blue", "10", "2020" },
{ "Jose Lemon", "25", "2016" }
};
std::string sortedByName[5][3];
sortString(students, sortedByName, size);
return 0;
}
，但我强烈建议您使用数组，向量和结构/类。按照矢量和阵列以及向量和构造的示例
#include <iostream>
#include <string>
#include <vector>
#include <array>
#include <algorithm>
void sortString(std::vector<std::array<std::string, 3>>& students)
{
// for example: print all names with range base for loop
for (const auto& s : students)
{
std::cout << s[0] << std::endl;
}
// for example: print all names with "normal" for loop
for (std::size_t i = 0; i < students.size(); ++i)
{
std::cout << students[i][0] << std::endl;
}
// sort by name
std::sort(std::begin(students), std::end(students), [](const std::array<std::string, 3>& a, const std::array<std::string, 3>& b){ return a[0] < b[0]; });
}
int main()
{
int const size = 5;
std::vector<std::array<std::string, 3>> students;
students.push_back({ "Joe Lime", "15", "2019" });
students.push_back({ "Bob Green", "3", "2020" });
students.push_back({ "SallyAnne Green", "1", "2017" });
students.push_back({ "SallyAnne Green", "1", "2017" });
students.push_back({ "Jose Lemon", "25", "2016" });
sortString(students);
return 0;
}
结构：
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
struct Student
{
std::string name;
std::string dontKnow;
std::string year;
};
void sortString(std::vector<Student>& students)
{
// for example: print all names with range base for loop
for (const auto& s : students)
{
std::cout << s.name << std::endl;
}
// for example: print all names with "normal" for loop
for (std::size_t i = 0; i < students.size(); ++i)
{
std::cout << students[i].name << std::endl;
}
// sort by name
std::sort(std::begin(students), std::end(students), [](const Student& a, const Student& b){ return a.name < b.name; });
}
int main()
{
int const size = 5;
std::vector<Student> students;
students.push_back({ "Joe Lime", "15", "2019" });
students.push_back({ "Bob Green", "3", "2020" });
students.push_back({ "SallyAnne Green", "1", "2017" });
students.push_back({ "SallyAnne Green", "1", "2017" });
students.push_back({ "Jose Lemon", "25", "2016" });
sortString(students);
return 0;
}
希望您看到您的代码获得多少清洁
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