How do you find the time complexity of a given algorithm?

Time complexity gives an indication of the time an algorithm will complete its task. However, it is merely an indication; two algorithms with the same time complexity won't necessarily take the same amount of time to complete. For instance, comparing two primitive values is a constant-time operation. Swapping those values is also a constant-time operation, however a swap requires more individual operations than a comparison does, so a swap will take longer even though the time complexity is exactly the same.