A Common-Sense Guide to Data Structures and Algorithms

We can never say with definitiveness that any operation takes, say, five seconds. While the same operation may take five seconds on a particular computer, it may take longer on an older piece of hardware, or much faster on the supercomputers of tomorrow. Measuring the speed of an operation in terms of time is flaky, since it will always change depending on the hardware that it is run on. However, we can measure the speed of an operation in terms of how many steps it takes. If Operation A takes five steps, and Operation B takes 500 steps, we can assume that Operation A will always be faster than Operation B on all pieces of hardware. Measuring the number of steps is therefore the key to analyzing the speed of an operation. Measuring the speed of an operation is also known as measuring its time complexity. Throughout this book, we’ll use the terms speed, time complexity, efficiency, and performance interchangeably. They all refer to the number of steps that a given operation takes.