The key idea is that if the adjacent characters are equal, then we can untangle them. So if a sequence of length n exists, we can change it to a sequence of length n-2 by deleting the adjacent ones.

For example, (-++-) -> (--) -> ()

I used a stack to do this.

• If the stack is empty, push the current character onto the stack.

• Else if the top symbol is same as the current one, pop it off the stack.

• Else push it onto the stack.

• Finally check if the stack is empty or not.

code