one of the practice problem have struct me off

here is the problem link i jst checked the solution and found that if we sort the array first check

as array is sorted

for(third=N-1;third>1;third–)

{

first=0;

second=third-1;

while(second>first)

{

if(len[first]+len[second]<len[third])

{

count+=second-first;

first++;

}

else

{

second–;

}

}

}

this part is the main logic for the given problem and this leads me in confusion how can we do this

count+=second-first;