Array of user defined size in C++

Here's the modified program. Hope you like!

#include <iostream> void calculateCharges(int); int main(){ int Num; std::cout<<"Enter Number of customers: "; std::cin>>Num; calculateCharges(Num); } void calculateCharges(int Num){ int NumOfCustomers = Num; double *hrs, *charges; // placeholder for dynamic array hrs = new double[NumOfCustomers]; charges = new double[NumOfCustomers]; double Total_hrs=0; double Total_charges=0; for(int i=0;i<NumOfCustomers;i++){ std::cout<<"Enter hours parked: "; std::cin>>hrs[i]; } for(int i =0;i<NumOfCustomers;i++){ if(hrs[i]<=3) charges[i]=2; else if(hrs[i]>3) charges[i]=2+((hrs[i]-3)*.5); if(charges[i]>10) charges[i]=10; } std::cout<<"Car\tHours\tCharge\n"; for(int i=0;i<NumOfCustomers;i++){ std::cout<<i+1<<"\t"<<hrs[i]<<"\t"<<charges[i]<<"\n"; } for(int i=0;i<NumOfCustomers;i++){ Total_hrs += hrs[i]; Total_charges += charges[i]; } std::cout<<"Total\t"<<Total_hrs<<"\t"<<Total_charges<<"\n"; delete [] hrs; delete [] charges; } 

You can use a std::vector, which is a class that enables efficient variable length arrays and relief you from manual allocation (you could still use double hrs = new double[NumOfCustomers]; delete [] hrs but this requires manual memory management and you don't want it.)

You can even use a single struct like:

struct CustomerData { double hrs; double charges; } std::vector<CustomerData> data(NumOfCustomers); .. std::for_each(data.begin(), data.end(), [](CustomerData &item) { item.charges = std::min(10, item.hrs <= 3 ? 2 : 2 + ((item.hrs-3)*.5)); }); 

You cannot have arrays of variable width. Array size should be known during during compilation. Either they need to be constant or some define parameter.

int a[10] 

OR

`define A_SIZE 10 int a [A_SIZE] 

std::vector is a STL container that is like an array but can change its size dynamically.

Reference on vectors.

http://www.cplusplus.com/reference/vector/vector/

A simple dynamic memory allocation can be done using c++.Let me show a small snippet regarding dynamic mem allocation.A pointer variable is allocated an integer array with new keyword.Then the memory allocate is deleted after we have completed the required process. NOTE:Dynamic memory allocation uses heap memory part.

#include <iostream> using namespace std; int main() { int size; cout<<"enter ur array size "<<endl; cin >> size; int *ash; ash = new int[size]; for (int i=0;i<size;i++){ cin >> ash[i]; } for (int j=0;j<size;j++){ cout << ash[j]<<endl; } delete[] ash; }