你知道如何在 C++ 中对多维数组进行排序吗？
我的输入是这样的：
Bogaerts_X 144 12 138
Cespedes_Y 51 5 48
Gomes_J 78 6 70
Holt_B 106 4 98
Napoli_M 119 17 133
Nava_D 113 4 81
Ortiz_D 142 35 95
Pedroia_D 135 7 75
Pierzynski_A72 4 40
Ross_D 50 7 58
我想按照第4列降序排列，我的代码包括sort()函数是这样的：
#include <iostream>
#include <fstream> //Required for fin.open, fin.close, fout.open, fout.close
#include <cstdlib> //Required for srand(), rand().
#include <ctime> //Required for time(NULL) to seed the random num gen
using namespace std;
// Declaration of the main function
int main()
{
ofstream fout;
ifstream fin;
string array[100][100];
int limit(0);
fin.open("312.txt" );
cout << " -------------------------------" << endl << endl;
for (int i=0; i<12; ++i) //every row
{
for (int j=0; j<4; ++j )//every col
{
fin >> array[i][j];
}
}
for (int i=0; i<12; ++i) //every row
{
for (int j=0; j<4; ++j )//every col
{
cout << "\t" << array[i][j];
}
cout << endl;
}
//sort players according to the 4th column
//Asks the user for a limit of home runs to search by
cout << "Give me the limit of home runs to search by"<<endl;
cin >> limit;
//sorted alphabetically and displays
for (int i=0; i<limit; ++i) //every row
{
for (int j=0; j<4; ++j )//every col
{
cout << "\t" << array[i][j];
}
cout << endl;
}
fin.close();
cout << endl << endl << endl << endl << endl << endl << endl;
// Exit program.
return 0;
}
//This sample function sorts the array with n elements
//into ascending order using selection sort
void sort(const double a[], int n)
{
double temp; int m; int x[0];
for (int k=0; k<=n-2; ++k) {
//find position of smallest element beginning at k
m = k;
for (int j=k+1; j < n-1; ++j)
if (a[j] < a[m])
m = j;
//exchange smallest value with value at k
temp = x[m];
x[m] = x[k];
x[k] = temp;
} //end for (k)
} //end sort()
如何使用这个排序功能按第4列排序？我真的很困惑......
当项目被分组到某种结构中时，对它们进行排序要容易得多。
struct Data
{
std::string name_;
int x_, y_, z_;
};
int main()
{
std::vector<Data> data;
Data d1 = { "Bogaerts_X", 144, 12, 138 };
Data d2 = { "Cespedes_Y", 51, 5, 48 };
data.push_back(d1);
data.push_back(d2);
std::sort(std::begin(data), std::end(data), [](const Data& a, const Data& b)
{
// sort based on the last member variable or 4th column in your case
return a.z_ < b.z_;
});
return 0;
}
数组没有复制赋值运算符。因此，您需要更改用于存储数据的数据结构。
这里显示了一个使用标准数据结构的方法
std::array#include <iostream>
#include <array>
#include <algorithm>
#include <string>
#include <iterator>
int main()
{
std::array<std::string, 4> data[] =
{
{ { "Bogaerts_X", "144", "12", "138" } },
{ { "Cespedes_Y", "51", "5", "48" } },
{ { "Gomes_J", "78", "6", "70" } },
{ { "Holt_B", "106", "4", "98" } },
{ { "Napoli_M", "119", "17", "133" } },
{ { "Nava_D", "113", "4", "81" } },
{ { "Ortiz_D", "142", "35", "95" } },
{ { "Pedroia_D", "135", "7", "75" } },
{ { "Pierzynski_A", "72", "4", "40" } },
{ { "Ross_D", "50", "7", "58" } }
};
for ( const auto &row : data )
{
for ( const auto &s : row ) std::cout << s << ' ';
std::cout << std::endl;
}
std::cout << std::endl;
std::sort( std::begin( data ), std::end( data ),
[]( const auto &a, const auto &b )
{
return std::stoi( a[a.size() - 1] ) < std::stoi( b[b.size() - 1] );
} );
for ( const auto &row : data )
{
for ( const auto &s : row ) std::cout << s << ' ';
std::cout << std::endl;
}
}
程序输出为
Bogaerts_X 144 12 138
Cespedes_Y 51 5 48
Gomes_J 78 6 70
Holt_B 106 4 98
Napoli_M 119 17 133
Nava_D 113 4 81
Ortiz_D 142 35 95
Pedroia_D 135 7 75
Pierzynski_A 72 4 40
Ross_D 50 7 58
Pierzynski_A 72 4 40
Cespedes_Y 51 5 48
Ross_D 50 7 58
Gomes_J 78 6 70
Pedroia_D 135 7 75
Nava_D 113 4 81
Ortiz_D 142 35 95
Holt_B 106 4 98
Napoli_M 119 17 133
Bogaerts_X 144 12 138
如果你想按降序对数组进行排序，那么 std::sort 的调用看起来像
std::sort( std::begin( data ), std::end( data ),
[]( const auto &a, const auto &b )
{
return std::stoi( b[b.size() - 1] ) < std::stoi( a[a.size() - 1] );
} );
如果您的编译器不支持 lambda 表达式中的 auto，那么您必须明确指定参数的类型
[]( const std::array<std::string, 4> &a, const std::array<std::string, 4> &b )
你也可以考虑使用一组
std::tuple当然，您可以使用标准类
std::vector您的目标：按第 4 列对记录（我的意思是一行是一条记录）进行排序。所以下一步是如何表示每条记录，显然， 你需要一个组合类型来表示记录；例如：（伪代码）
class Record{
//成员变量
char *name;
int age;
int date;
float score;
Record(){/* constructure */}
~Record(){/* distructure*/}
//成员函数
void sort(/*arguments*/){/*bubble sort . selection sort . quick sort*/}
};下一个方法不可取： 在二维数组中，一条记录就是一维数组，例如，arr[0][0] arr[0][1] arr[0][2] arr[0][3] 表示第一条记录，同时, arr[0] 代表 string[4] ！你有什么灵感吗？以下是伪代码：
void bubble_sort(string ** array, int first_dimension_length, int sort_column){
string mini = "2100000000";
int mini_row = 0;
string * swap = NULL;
for(int i = 0; i < first_dimension_length; ++i){
for(int j = i + 1; i < first_dimension_length; ++j){
if(mini > array[j][sort_column]){
mini = array[j][sort_column];
mini_row = i;
}
}
swap = array[i];
// swap point to one dimension array, that's swap is a pointer
array[i] = array[mini_row];
//array[i] also point to one dimension array
array[mini_row] = swap;
//array[mini] also point to one dimension array
}
}一句话，第一种方法值得你尝试;
struct Data
{
std::string name_;
int x_, y_, z_;
};
int main()
{
std::vector<Data> data;
Data d1 = { "Bogaerts_X", 144, 12, 138 };
Data d2 = { "Cespedes_Y", 51, 5, 48 };
data.push_back(d1);
data.push_back(d2);
std::sort(std::begin(data), std::end(data), [](const Data& a, const Data& b)
{
// sort based on the last member variable or 4th column in your case
return a.z_ < b.z_;
});
return 0;
}