Как отсортировать массив структур?

Question

Мне нужно использовать сортировку сортировки для сортировки массива структур в порядке убывания суммы. Я застрял на этом в течение часа и ничего не нашел, любая помощь была бы высоко оценена.

Это текстовый файл, я использую

Cola 
0.75 20 
Ruby Red Blast 
1.00 10 
Lemon Fizz 
0.75 8 
Grape Soda 
0.90 5 
Citrus Flip 
0.85 0 
Habanero Surprise 
0.80 11 

Вот мой код

#include <iostream> 
#include <fstream> 
#include <iomanip> 
#include <string> 

using namespace std; 




struct soda1{ 
    string name; 
    double price; 
    int amount; 
}; 

typedef soda1 soda[6]; 

void vendingmachine(struct soda1[6]); 



int main(){ 
ifstream inFile; 
int SIZE=6; 
soda soda; 
double profit=0; 



inFile.open ("machine.txt"); 
if (inFile.fail()) 
{ 
    cout << "Error: Data file could not be opened" << endl; 
    exit (EXIT_FAILURE); 
} 

for(int i=0; i < SIZE; i++){ 
    getline(inFile, soda[i].name); 
     inFile >> soda[i].price; 
     inFile >> soda[i].amount; 
     inFile.ignore(100,'\n'); 
} 


    cout << "Welcome to the vending machine!" << endl; 
    cout << endl; 



    cout << "***************************************************************" << endl; 
    cout << "  " << "Drink Name" << "  " << "Price Per Can" << "   " << "Number in Machine" << endl; 

    for(int i=0; i < SIZE; i++){ 

     cout << setw(17) << soda[i].name << setw(16) << soda[i].price << setw(20) << soda[i].amount << endl; 
    } 
    cout << "***************************************************************" << endl; 


    int choice; 
    cout << "Please press 1-6 for a drink or 0 if you wish to quit: "; 
     cin >> choice; 
     if((choice!=0) && (choice!=1) && (choice!=2) && (choice!=3) && (choice!=4) && (choice!=5) && (choice!=6)){ 
      cout << "Error invalid choice" << endl;} 
     while((choice >=1) && (choice <=6)){ 


      if((choice==1) && (soda[0].amount!=0)){ 
       cout << endl << "Please input $1.00 for your beverage" << endl; 
       cout << "Change is .25" << endl; 
       soda[0].amount--; 
       profit = profit+.25; 
       } 
      if((choice==1) && (soda[0].amount==0)){ 
        cout << "Sold Out" << endl; 
       } 
      if((choice==2) && (soda[1].amount!=0)){ 
       cout << endl << "Please input $1.00 for your beverage" << endl; 
       cout << "Change is 0" << endl; 
       soda[1].amount--; 
       profit = profit+.25; 
       } 
      if((choice==2) && (soda[1].amount==0)){ 
        cout << "Sold Out" << endl; 
       } 
      if((choice==3) && (soda[2].amount!=0)){ 
       cout << endl << "Please input $1.00 for your beverage" << endl; 
       cout << "Change is .25" << endl; 
       soda[2].amount--; 
       profit = profit+.25; 
       } 
      if((choice==3) && (soda[2].amount==0)){ 
        cout << "Sold Out" << endl; 
       } 
      if((choice==4) && (soda[3].amount!=0)){ 
       cout << endl << "Please input $1.00 for your beverage" << endl; 
       cout << "Change is .10" << endl; 
       soda[3].amount--; 
       profit = profit+.25; 
       } 
      if((choice==4) && (soda[3].amount==0)){ 
        cout << "Sold Out" << endl; 
       } 
      if((choice==5) && (soda[4].amount!=0)){ 
       cout << endl << "Please input $1.00 for your beverage" << endl; 
       cout << "Change is .15" << endl; 
       soda[4].amount--; 
       profit = profit+.25; 
       } 
      if((choice==5) && (soda[4].amount==0)){ 
        cout << "Sold Out" << endl; 
       } 
      if((choice==6) && (soda[5].amount!=0)){ 
       cout << endl << "Please input $1.00 for your beverage" << endl; 
       cout << "Change is .20" << endl; 
       soda[5].amount--; 
       profit = profit+.25; 
       } 
      if((choice==6) && (soda[5].amount==0)){ 
        cout << "Sold Out" << endl; 
       } 


    vendingmachine(soda); 
     cout << "Please press 1-6 for a drink or 0 if you wish to quit: "; 
     cin >> choice; 
     } 
     cout <<"The Profit is: " << profit << endl; 




return 0; 
} 

void vendingmachine(struct soda1 soda[6]){ 



    cout << "***************************************************************" << endl; 
    cout << "  " << "Drink Name" << "  " << "Price Per Can" << "   " << "Number in Machine" << endl; 

    for(int i=0; i < 6; i++){ 

     cout << setw(17) << soda[i].name << setw(16) << soda[i].price << setw(20) << soda[i].amount << endl; 
    } 
    cout << "***************************************************************" << endl; 

} 

Answer 1

Вы можете использовать std::sort из <algorithm> заголовка:

std::sort(&soda[0], &soda[6], 
    [](soda1 left, soda1 right) { 
     return left.amount > right.amount; // > = descending, < = ascending 
    }); 

Или, если вы не нет лямбда-функций:

bool sortSoda(soda1 left, soda1 right) { 
    return left.amount > right.amount; // > = descending, < = ascending 
} 

//... in int main() 
std::sort(&soda[0], &soda[6], sortSoda);