Subset Problem Easy sum

#1

#include
using namespace std;
int main()
{
int sum;
int t;
cin>>t;
while(t>0)
{
int n;
cin>>n;
int arr[n];
for(int i=0;i<n;i++)
{
cin>>arr[i];
}
for(int i=0;i<n;i++)
{
for(int j=i;j<n;j++)
{
sum=0;
for(int k=i;k<=j;k++)
{
sum=sum+arr[k];
}
if(sum==0)
{
cout<<“Yes”<<endl;
break;

            }
            else if(i==n-1)
            {
                cout<<"No";
            }
            
        }
    }
    
    t--;
}
return 0;

} There is a minute mistake in the code because NO is printing i dont know pls tell me…

#2

Hi Aryan
You are approaching this problem wrong. The problem is about subsets(or subsequences) , not subarrays.
Subarrays are parts of array that are continuous while subsets may or may not be continuous .
We are supposed to consider the subsets in this problem.

For example for an array a[ ] = {1 , 2 , 8 ,-3 } has a subset { 1 , 2 , -3 } which gives sum as 0 and should hence print “Yes” . However your code would give “No” since it does not consider non-continuous subsets.

Use recursion to generate all possible subsets of the array and calculate the sum . Since it is mentioned that the size of array won’t exceed 4 , recursion wouldn’t take much time for such a small array.
If the sum of any one such subset is zero , print “yes” , else “No” .

Use a boolean flag variable to mark it so . That should help you in this code as well if you just want to consider the subarrays.
Initialise flag as false. Mark it true if a subset has sum 0. After the loop if flag== true , print “Yes” , else “No” . Its important that you check after the loop/recursive call and not in it otherwise it could give you some problems.

#3

bool comparator(string a, string b) { if (a.find(b)==0 || b.find(a)==0) return a.length() > b.length(); return a < b; }

#4

can you please tell me how this comparator is working.

#5

This comparator first checks whether either of the strings is a prefix substring of the other one.
For example :
“abc” is a prefix substring of “abcdef” or “abcd” or any other string starting with “abc”.
If any of the two strings is a prefix substring of the other , the longer string comes first .

Otherwise , if neither of the strings are a prefix substring of the other then the comparator simply compares them normally … comparing ASCII values character by character.

Refer to this for a simple example - https://ide.codingblocks.com/s/91032

#6

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