add is work but minus doesnt work

[alitt]

hi
this is my code with function, it works when adding numbers but when i change line 27 to minus (like this sum-=a[i])answer is 0

#include <iostream>
using namespace std;

int add(int[]);

int main(){
	
	int num[3];
	
	for(int i=0;i<3;i++){
		
		cout<<"enter number: ";
		cin>>num[i];
	}
	
	cout<<add(num);
	
	return 0;
}

int add(int a[]){
	
	int sum;
	for(int i=0;i<3;i++){
		
		sum+=a[i];
	}
	return sum;
}

[Peter87]

You forgot to initialize sum.

[Thomas1965]

The problem is in line 23:
int sum;
You need to initialize it before you can use it;

[alitt]

thank you so much
but i didnt understand
where should i initialize sum?

[Thomas1965]

Best is to do it when you declare it: int sum = 0;

[alitt]

i have changed to this
sorry for my amateur question

#include <iostream>
using namespace std;

int min(int[]);

int main(){
	
	int num[3];
	
	for(int i=0;i<3;i++){
		
		cout<<"enter number: ";
		cin>>num[i];
	}
	
	cout<<min(num);
	
	return 0;
}

int min(int a[]){
	
	int sum=0;
	for(int i=0;i<3;i++){
		
		sum-=a[i];
	}
	return sum;
}

[alitt]

it doesnt work

[TarikNeaj]

Worsk fine for me.

Input: 5,6,7
output: -18.

input: 2,2,2
output: -6

[alitt]

im gonna calculate 10-1-1=8
thanks

[TarikNeaj]

Then maybe you should change your code so it doesn't minus everything.

sum-=a[i];

Every number that is in the array will be reversed. If it is 5, -5 will go into sum. So change your code to make it do what you want. Which apparently is to not reverse the first number, but only the second and third.

[alitt]

thanks for helping
im little confused
i dont know how to minus these numbers

[TarikNeaj]

You are already minusing them? But right now you're minusing all 3. You want to minus only the last 2 digits, not the first one.

[alitt]

thanks
yes im gonna minusing them
understood
so how can i minus last 2 numbers?

[TarikNeaj]

Your code already minuses 3 numbers. Now take a thinker and make it minus 2 numbers instead of 3, it should not be very hard if you actually try, which you are not right now. Work on it yourself and you'll learn more.

[alitt]

i think more
thanks for answering

[Peter87]

Note that if you use += you can calculate 10-1-1 by inputting the numbers 10, -1 and -1.

[elaleph]

This works for you?

#include <iostream>

int add( int a[] ) ;

int main()
{	
	int num[3] ;
	
	for( int i = 0; i < 3; ++i)
	{	
		std::cout << "enter number: " ;
		std::cin >> num[i] ;
	}
	
	std::cout << add( num ) ;
	
	return 0 ;
}

int add( int a[] )
{
	int sum = a[0] ;
	
	for( int i = 1; i < 3; ++i )
	{
		sum -= a[i] ;
	}
	
	return sum ;
}

[jgg2002]

@elalelph is right.