I'm implementing the zigzag search strategy for the Lost Cow problem. Farmer John starts at x and searches at positions x+1, x-2, x+4, x-8, and so on, doubling the distance from the original starting point each time while alternating direction. My code works for some tests, such as 1 5, but fails others. For example, input 1 6 produces 25, which seems incorrect. Could someone point out what is wrong with my approach?
3 Answers
A useful way to structure the solution is to save `start = x`, then repeatedly choose a target offset of 1, -2, 4, -8, and so on. Move only until reaching the target or passing Bessie, adding the distance traveled each time. Avoid modifying the saved starting position, and print the current position, target, direction, and total distance while debugging. This makes errors in the zigzag pattern much easier to spot.
You have hardcoded the starting position into this line: `target = 3 + op`. That only works when the original x value is 3. The target should be calculated from the unchanged starting position, such as `target = start + direction * distance`. Keep the original x in a separate variable because the current position changes as you walk.
Use descriptive variables and avoid calculating targets from changing state. For example, maintain `current`, `start`, `step`, and `total`. On each round, set the target to `start + step`, move toward it, then double and reverse `step`. The important detail is that every search endpoint is measured from the initial position, not from wherever Farmer John currently stands.
I accidentally hardcoded 3 because I was testing the sample input. I changed it to use the original starting position, and that fixed the problem. Thanks!