i am getting Segmentation fault

Question

#include <bits/stdc++.h>
#define ll long long
using namespace std;

int main() {
int t;
cin>>t;

while(t--)
{
    ll n, a[10000000];
    cin>>n;

    for(int i=0;i<n;i++)
    cin>>a[i];

    for(int i=0;i<n-1;i++)
    {
        int flag=0;
        for(int j=i+1;j<n;j++)
        {
            if(a[j] > a[i])
            {
                cout<<a[j]<<" ";
                flag=1;
                break;
            }
        }

        if(flag==0)
         cout<<"-1 ";
}
cout<<"-1\n";
}
return 0;
}

why i am getting segmentation fault using this code? is there anything wrong in the code. as per my knowledge there is nothing wrong in code. please do explain the fault...

https://stackoverflow.com/questions/31816095/why-should-i-not-include-bits-stdc-h — , Mar 18 '19 at 14:23
Unrelated to your segmentation fault (which is absolutely _full_ of information you can examine in a debugger), there is at least one thing wrong in your code: don't include ``, it's an internal implementation detail. — Useless, Mar 18 '19 at 14:26
if you ever plan to write code professionally please avoid the first three lines of your code. — drescherjm, Mar 18 '19 at 14:26
I get that there are a lot of bad tutorials online that propagate `using namespace std;` and `#include ` but I don't understand why I keep seeing `#define ll long long`. — François Andrieux, Mar 18 '19 at 14:27
@drescherjm yes! so i have used those short hands to save time. but i could see majority of comments suggesting to avoid this practice..... — Gowtham Gowda, Mar 18 '19 at 14:36
I use `int64_t` when I need a 64 bit integer at work. https://en.cppreference.com/w/cpp/types/integer — drescherjm, Mar 18 '19 at 14:47
Interesting thing about using shortcuts to save time: Proving that they are indeed shortcuts can take a lot of time. — user4581301, Mar 18 '19 at 14:50

Bathsheba · Answer 1 · 2019-03-18T14:35:31.903

1

a[10000000] is probably too large to have automatic storage duration. Regard something of the order of 1Mb as the limit.

The fix is to replace the first two lines of your loop with

std::size_t n; // using a macro is a bad idea
std::cin >> n; // no professional programmer uses `using namespace std`
std::vector<long long/*using a macro is a bad idea*/> a(n);

noting that you ought to deal with any exceptions to the std::vector construction if n is too large.

edited Mar 18 '19 at 14:35

answered Mar 18 '19 at 14:23

Bathsheba

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`a(10000000);` should be moved to be after the input of `n` and then just use `a(n);` – NathanOliver Mar 18 '19 at 14:33
@NathanOliver ya. that would be executed at run time. – Gowtham Gowda Mar 18 '19 at 14:38

i am getting Segmentation fault

1 Answers1