Poor Pigs
To solve this coding challenge, the primary goal is to determine the minimum number of pigs required to identify the single poisonous bucket among several buckets of liquid within a certain time frame. Hereβs a step-by-step explanation of how to approach this problem logically and derive the solution:
Explanation:
- Understanding the Problem:
- You have a number of buckets, with exactly one bucket containing poison.
- We have a limited number of pigs and a set amount of time to determine which bucket is poisonous.
- Each pig can drink from multiple buckets, but once a pig drinks from a poisonous bucket and dies, it cannot be reused.
-
You can perform tests in cycles, where each cycle takes
minutesToDie
minutesToTest
- Formulating the Problem:
- The pigs, when drinking from the buckets, act as binary sensors (alive or dead).
- Each pig can give us a bit of information depending on whether it survives after drinking from a set of buckets.
-
The total number of tests we can perform is
minutesToTest // minutesToDie
- This means each pig can provide more than one bit of information through multiple cycles.
- Deriving the Formula:
-
To determine the number of pigs required, we consider the number of possible states. Given
states = (minutesToTest // minutesToDie) + 1
-
If we have
k
states
states^k
- We need this number of combinations to be at least equal to the number of buckets to ensure we can distinguish each bucket.
-
We need to find the smallest number of pigs
k
(minutesToTest // minutesToDie + 1)^k >= buckets
- Solution Approach:
-
We incrementally increase the number of pigs
k
(minutesToTest // minutesToDie + 1)^k >= buckets
-
The number of pigs
k
- Initialize Variables:
-
Start with
numberOfPigs
- Calculate States:
-
Calculate the number of states each pig can represent using the formula
states = (minutesToTest // minutesToDie) + 1
- While Loop to Find Minimum Pigs:
-
Enter a loop that continues until the condition
(states^numberOfPigs) >= buckets
- This loop ensures we keep adding pigs incrementally until their combined states are sufficient to identify the poisonous bucket.
- Increment Number of Pigs:
-
Inside the loop, increment the
numberOfPigs
- Return Result:
-
Once the loop terminates, return the
numberOfPigs
Pseudocode with Comments
# Function to calculate minimum number of pigs needed
function calculateMinimumPigs(buckets, minutesToDie, minutesToTest)
# Initialize the number of pigs to 0
numberOfPigs = 0
# Calculate the number of cycles we can perform
states = (minutesToTest // minutesToDie) + 1
# While the total number of buckets that can be tested by the current number of pigs is less than the required buckets
while states^numberOfPigs < buckets
# Increment the number of pigs
numberOfPigs += 1
# Return the minimum number of pigs found
return numberOfPigs
# Example Usage
buckets = 4
minutesToDie = 15
minutesToTest = 15
output = calculateMinimumPigs(buckets, minutesToDie, minutesToTest)
print(output) # Expected output: 2