Need help in BRCKTS - Brackets(SPOJ)

Problem link
My code
This approach is giving wrong answer.
Can you please help me out in this question.
My approach is something like:-
Now I am just checking two conditions.
1.Is the overall sum of the segment is 0 or not because a balanced segment like (()) will be (+1+1-1-1)=0.
2.Now to avoid the conditions like )( , (( , I am checking whether the left child node of the 1st node is having sum>=0 and right child sum<=0.If this gets true , then answer is yes else no.
Thanks in advance.
EDIT: My approach will fail in a testcase like

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