我有一个双维std :: string数组，我需要将其作为函数 sortString 的参数传递，但是在首次读取变量 student 时出现运行时错误。 “0”通过cout输出，但不是“1”。知道我哪里错了吗？
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------------ **
我想对一维数组做同样的事情，所以我不明白它为什么不能用于二维数组
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;
}
答案 0 :(得分：1)
你对数组，指针和字符串有很大的困惑。作为@Quentin和 @molbdnilo指出你，你正在进行从std :: strings的二维数组到指向字符串指针的指针的C风格转换，并且数组既不是指针也不是指针都是数组。
我的猜测是，您希望根据姓名对所有学生进行排序，同时保留与相应学生相关的其余学生信息。
一些建议：
您尝试实现的example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
Bob Green 3 2020
Joe Lime 15 2019年 Jose Lemon 25 2016年
SallyAnne Green 2017年1月
答案 1 :(得分：1)
我修改了你的代码并让它工作：
#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。下面用矢量和数组以及矢量和结构组成一个例子
#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;
}
with struct：
#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;
}
我希望你看到你的代码有多清洁