How to find the highest number of passenger of all round? - c++

Question

im a new problem solver. recently i came across this problem on codeforces website. i managed to get the two values required for each turn depending on the number of turn given by the user, but i cant find the highest number of passenger at stop out of all.
#include <iostream>
#include<cstring>
#include<algorithm>
using namespace std;
int main()
{
int turn,get_off,get_on,total_passenger,highest_total;
cin>>turn;
int* stops=new int(turn);
for(int i=0;i<turn;i++){
cin>>get_off>>get_on;
total_passenger=get_on-get_off;
stops[i]=total_passenger;
}
for(int i=0;i<turn;i++){
if(stops[i]>stops[i+1]){
highest_total=stops[i];
}
}
cout<<highest_total<<endl;
return 0;
}

Answer 1

you can try using https://en.cppreference.com/w/cpp/algorithm/max_element
also you set the total passengers number to the difference between get off and get on and I think you should just add that difference, and to allocate memory for int* you use [] instead of ()
#include <iostream>
#include<cstring>
#include<algorithm>
using namespace std;
int main()
{
int turn,get_off,get_on,total_passenger,highest_total;
cin>>turn;
int* stops=new int[turn];
for(int i=0;i<turn;i++){
cin>>get_off>>get_on;
total_passenger+=get_on-get_off;
stops[i]=total_passenger;
}
cout<<std::max_element(stops, stops + turn)<<endl;
}

Answer 2

The issue seems to be with int *stops = new int(turn). It will allocate memory for 1 integer.
Use int stops[turn] and your algorithm need to be modified.
stop[i] += total_passenger need to be used with some if-else.

Answer 3

You can initiate stops as an array I guess(int stops[turn]) as C++ now offers to allocate memory this way even inside any function. That may solve your problem.
Alongside you will have to check corner cases as your highest_total variable may provide garbage value. So while declaring the variable assign a value to it. I prefer initializing int highest_total=-1 here.
Actually you dont need an array or pointer here. This can be solved this way-
#include<cstring>
#include<algorithm>
using namespace std;
int main()
{
int turn,get_off,get_on,total_passenger=0;
cin>>turn;
int highest_total=-1;
for(int i=0;i<turn;i++){
cin>>get_off>>get_on;
total_passenger=total_passenger+get_on-get_off;
if(total_passenger>highest_total)
highest_total=total_passenger;
}
cout<<highest_total<<endl;
return 0;
}

Answer 4

Firstly: int* stops=new int(turn); initializes a pointer to a new int with the value turn. See int a = 0 and int a(0) differences
Instead you should either use int* stops=new int[turn];, read about when you should use new here: When should I use the new keyword in C++?. An important note is that you have to delete the variable in order to avoid a Memory leak.
Or (which I would say is the case you should use in this scenario), int stops[turn];.
Besides that I can not argue with your logic since I believe this is not a forum to help you solve code, although the syntax seems correct.
I would recommend reading Why is "using namespace std;" considered bad practice? if you are interested in learning C++ though.