There are two algorithms of determining a bridge in the graph: simple and advanced. Simple algorithm O(n^2) works more than 1s if written in Java, but less than 1s if written in C++.

I suggest to lower time limit to 0.5s, after that only advanced solutions O(n), (n=number of islands) will be accepted.

My first C++ solution O(n^n) runs about 0.3sec, so i think it's useless to decrease time limit.