Find the number in vector using Hash Table [closed]

I was doing a Competitive Programming Question and in that I have to find a number in a vector . We can Find the number or the next largest number. I used Binary Search to find that but the compiler is still showing a TLE Error. So I Researched and find out that Hash Table can perform searching in O(1). Can you Please tell me a way or help me out to find the number in less time than Binary Search. Thanks For The Help!