@s1d_3 Exactly a similar problem. Couldn’t find a test case where greedy should fail.
Alloted ( to the left place and ) to the right indices for all k. Then filled the remaining places wity alternate ( and).
Just 1 test case passed though. 
https://www.codechef.com/viewsolution/7956764
#include <bits/stdc++.h>
using namespace std;
char a[2001];
void complete(long st,long end,long size)
{
long b[size],j=0;
for(long i=st+1;i<end;i++)
{
if(a[i]!='(' && a[i]!=')')
{
b[j]=i;
j++;
}
}
for(long i=0,k=j-1;i<k;i++,k--)
{
a[b[i]]='(';
a[b[k]]=')';
}
}
void completefinish(long st,long end,long size)
{
long b[size],j=0;
for(long i=st;i<end;i++)
{
if(a[i]!='(' && a[i]!=')')
{
b[j]=i;
j++;
}
}
for(long i=0,k=j-1;i<k;i++,k--)
{
a[b[i]]='(';
a[b[k]]=')';
}
}
int main() {
int t;
cin>>t;
while(t–)
{
long long n,q,size,m=LLONG_MIN;
cin>>n>>q;
size=2q;
long l[size];
for(long i=0;i<2q;i=i+2)
{
cin>>l[i]>>l[i+1];
a[l[i]]=’(’;
a[l[i+1]]=’)’;
}
long j=0,k;
for(long i=0;i<q;i=i+2)
{
complete(l[i],l[i+1],(l[i+1]-l[i]));
}
completefinish(0,n,n);
for(long i=0;i<n;i++)
cout<<a[i];
cout<<endl;
}
return 0;
}
not geting why getting wrong anstion can anyone tell
The question asks to print any of the output. How does an online compiler checks every output?
Please tell us what is First and fifth test case or what is wrong with my approach its basically O(N) solution i guesslink text
Since there could be multiple possible answers for this problem…the tester’s algorithm only checks if the segment between ‘x’ and ‘y’ (exclusive) is balanced or not.Hence lot of incorrect solutions got accepted.
I don’t claim this to be correct but I suppose this may be.
Weak Test cases… My wrong solution got passed.
SORT THE RANGES in terms of their of difference.
and they apply the ranges on the decreasing order.
For sorting the range with key “difference of the range”, you may use a vector pair pair in c++.
I have solbed it using semaphore like logic in O(n) time
Please Check here
https://www.codechef.com/viewsolution/7963748
Please let me know whats wrong or can u please share test cases
1 Like
Can I know the solution of this test case,
8 3
1 6
0 3
4 7
I ran on few accepted solutions and found the solution is ()()()(). Now how can the sub-string with x = 1 and y = 6 is balanced for such a solution? Resulting sub-string is )()()( which is not balanced.
#include<stdio.h>
int main()
{
int t;
scanf("%d", &t);
while(t–)
{
int n, k;
scanf("%d %d", &n, &k);
int i, x[k], y[k], j;
char s[n];
for(i=0;i<k;i++)
scanf("%d %d", &x[i], &y[i]);
for(i=0;i<n;i++)
s[i]=’)’;
int c1, c2;
for(i=0;i<k;i++)
{
s[x[i]]=’(’ ;
s[y[i]]=’)’ ;
c1=1;
for(j=x[i]+1; j<y[i]; j++ )
{
if( s[j]==’(’ )
c1++;
else
c1–;
if(c1<0)
{
s[j]=’(’;
c1+=2;
}
}
}
for(i=0;i<n;i++)
printf("%c", s[i]);
printf("\n");
}
return 0;
}
The logic is very simple, solution in O(n*k) for the worst case.
someone has done it in o(k) complaxity by just sorting all given k values according to starting range value.
CodeChef: Practical coding for everyone.
can anyone explain that how this solution in correct mathematically?
Interesting! I just sorted the queries by start index (breaking ties by end index) and for each constraint I just alternated “(” and “)” from segm.begin to segm.end, overwriting any previous changes. Complexity is O(N * K), although I’m sure it can become O(N + K*log(N)) with some sort of segment trees.
Funny story. It got AC. Not sure why.
Here is my solution: link
Hi guys, I agree test cases for this problem were week. 
and I apologize for the same. I missed one case which lead to pass incorrect solutions, but it would not be fair to re-judge the problem. So, I will add that test case in the practice section, where you can check you solution.
while(t--)
{
char a[2001];
int n,k,x,y;
cin>>n>>k;
a[n] = '\0';
for(int i=0;i<k;i++)
{
cin>>x>>y;
a[x] = '(';
a[y] = ')';
bool isSet = 0;
for(int j = x+1;j<y;j++,isSet = !isSet)
{
if(!isSet)
a[j] = '(';
else
a[j] = ')';
}
}
cout<<a<<endl;
}
Why my solution fails can anyone give testcase on where it fails ??
Input
1
10 4
3 6
2 9
4 5
8 9
Output should be ((((()))()
but those codes like CodeChef: Practical coding for everyone and many others
giving output as ((()()()() are also accepted, which is wrong. So please rejudge
What is the problem with this code? Only the first substask is passing.
Please can u provide the test cases.
#include
#include
using namespace std;
int main()
{
long long int t,n,k,i,x,y;
cin>>t;
while(t–)
{
cin>>n>>k;
char arr[n];
for(i=0;i<n-1;i+=2)
{
arr[i]=‘(’;
arr[i+1]=‘)’;
}
// cout<<endl;
// cin>>x>>y;
// arr[x]=‘(’;
// arr[y]=‘)’;
// low=x;
// high=y;
//k=k-1;
while(k–)
{
cin>>x>>y;
for(i=x;i<y;i+=2)
{
//if(arr[i]==‘(’)
// break;
//else
{
arr[i]=‘(’;
arr[i+1]=‘)’;
}
}
//arr[x]='(';
//arr[y]=')';
//if(x<low)
// low=x;
// if(y>high)
//high=y;
}
/* c=0;
//cout<<high<<" "<<low<<endl;
mid=((high-low)+1)/2;
//cout<<mid<<endl;
for(i=0;i<low;i++)
arr[i]='(';
for(i=low;i<=high;i++)
{
if(arr[i]=='0' && c < mid)
{
arr[i]='(';
c++;
}
else if(arr[i]=='(')
c++;
else if(arr[i]==')')
c--;
else
{ arr[i]=')';
c--;
}
}
for(i=high+1;i<n;i++)
arr[i]=')';
//cout<<arr<<endl;*/
for(i=0;i<n;i++)
cout<<arr[i];
cout<<endl;
}
return 0;
}
I have never got so may wrong answers for a question as in this one.Still unable to find a test case where this fails.Please someone find a test case for me…I have matched with all the test cases of this page and all those cases works fine in my code…Link to my code:
https://www.codechef.com/viewsolution/7951755
In the column “Breaking down the partially intersecting constraints into simpler form:”
what if length of the segment [c,b] is odd?
I have to re-post it, but still the question in practice is still accepting the incorrect solutions and it gave wrong answer to my correct solution, that’s totally disappointing from the codechef…
Codechef should also not include this contest for calculating the rating coz it has an erroneous problem which gave many users including me WA during the contest and the actual in-correct solution were passed giving them AC… one way for codechef to improve and make up for their error…