Role of container in priority_queue of C++ STL.

Why vectors are used in container.

And what are advantages and disadvantages if I use deque instead of vector.

which is faster:

• Sorting a vector
• Or using a priority queue

I was solving problem link . My code runs fine on my other compilers. But It fails on same testcases on CF online Judge. Here is my solution link.[submission:112599418][submission:112599418] In the code, at one line I had checked if a double is integer or not. I am not able to figure out why is it happening so. Please help.