How to initialize structure to zero everytime in while loop?

Question

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define max 200005
struct st{
    ll index,freq,val;
}s[max];;

int main(){
    ll t;
    cin>>t;
    while(t--){
        ll n;
        cin>>n;
        ll counter[max]={0};
        for(ll i=1;i<=n;i++){
            ll x;
            cin>>x;
            s[x].val=x;
            s[x].index=i;
            s[x].freq++;
            cout<<s[x].freq<<endl;
        }
        
    }
    return 0;
}

In this code, how I will initialize struct to zero in every while loop. I have tried memset() but It is showing error. Also I created struct object in main function. But the program crashes. Please give me hints to solve the problem.

the first 4 lines of your code made me dizzy. Why are you writing code like that? — 463035818_is_not_an_ai, Nov 28 '20 at 16:37
[Why should I not `#include `?](https://stackoverflow.com/questions/31816095/why-should-i-not-include-bits-stdc-h) / [Why is “using namespace std;” considered bad practice?](https://stackoverflow.com/questions/1452721/why-is-using-namespace-std-considered-bad-practice). `typedef long long ll;` is just "wtf?!?", just don't do it. And macros are not to define constants — 463035818_is_not_an_ai, Nov 28 '20 at 16:38
^^ No worries, thats why I try to tell you whats wrong about it ;) — 463035818_is_not_an_ai, Nov 28 '20 at 16:39
@Surt I used `memset( &st, 0, sizeof(st) );` in first line after while loop. — shadril238, Nov 28 '20 at 16:43

score 2 · Answer 1 · answered Nov 28 '20 at 16:48

2

Try this instead, its more structured, usually less error prone.

std::fill(std::begin(s), std::end(s), st({0,0,0}));

I might even be converted to memset by the compiler.

answered Nov 28 '20 at 16:48

Surt

15,501
3
23
39

score 0 · Answer 2 · answered Nov 28 '20 at 16:49

0

Surely there will be a better solution than this but you can add this snippet at the beginning of the while loop:

for(int j=0; j<max; j++){
    s[j].val=0;
    s[j].index=0;
    s[j].freq=0;
}

You can also consider the idea of redeclaring the struct array every time in the loop, just like this:

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define max 200005
struct st{
    ll index,freq,val;
};

int main(){
    ll t;
    cin>>t;
    while(t--){
        st s[max];
        ll n;
        cin>>n;
        ll counter[max]={0};
        for(ll i=1;i<=n;i++){
            ll x;
            cin>>x;
            s[x].val=x;
            s[x].index=i;
            s[x].freq++;
            cout<<s[x].freq<<endl;
        }
        
    }
    return 0;
}

answered Nov 28 '20 at 16:49

Losak

26
4

This will explode in your face if max stack is less than 200005*sizeof(long long)*3 – Surt Nov 28 '20 at 16:50
I tried this method but it is showing tle – shadril238 Nov 28 '20 at 16:54
@the_noobie_coder What is tle? Not everyone follows competitive programming. – Blastfurnace Nov 28 '20 at 16:57
C++ developers usually get accustomed to using std::cin and std::cout for standard I/O operations, but they aren’t the fastest ones out there. If you are feeling lazy to change your code, you can… – QuentinUK Nov 28 '20 at 17:03

score 0 · Answer 3 · answered Nov 28 '20 at 17:02

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define max 200005
struct st{
    ll index,freq,val;
};

int main(){
    ll t;
    cin>>t;
    while(t--){
        st s[max]={0};
        ll n;
        cin>>n;
        ll counter[max]={0};
        for(ll i=1;i<=n;i++){
            ll x;
            cin>>x;
            s[x].val=x;
            s[x].index=i;
            s[x].freq++;
            cout<<s[x].freq<<endl;
        }
        
    }
    return 0;
}

I did this. The problem is solved. I used dev c++ ide, that's why the code was doing problem. Thanks all

How to initialize structure to zero everytime in while loop?

3 Answers3