various C++ main() signatures and their efficiency

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Recently I came across the below given code on a competetive programming website,

   #include<bits/stdc++.h> using namespace std; #define int long long #define mp make_pair #define pb push_back #define d double #define FAST ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);  signed main() { return 0; //Omitted the rest of the code } [Full Code][1]

I would like to know what's the difference between this code and a regular C++ code with int main() in terms of efficiency and performance in terms of CPU speed, The problem sets are often huge.


signed main() is equivalent to int main() unless - like in the example - you have a macro which defines int as long long. main() has to return an int but the macro #define int long long means using the syntax int main() in this case will not compile with an error stating ::main must return int. Hence, signed main().


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