Incremental Memory Leak

Incremental Memory Leak

What is this problem about?

The Incremental Memory Leak coding problem simulates a scenario with two memory sticks. Every second $i$ (starting from $i=1$), the system attempts to allocate $i$ units of memory. The system always picks the stick with more available memory. If both have equal memory, it picks the first stick. The simulation ends when neither stick has at least $i$ units available. You need to return the time when the program crashes and the remaining memory on both sticks.

Why is this asked in interviews?

TikTok and other companies use this to test basic simulation skills and loop control. It evaluates whether you can follow a set of rules accurately and handle the state transitions of multiple variables. It’s a test of "Clean Simulation"—writing a loop that clearly reflects the problem description without introducing errors in the comparison logic.

Algorithmic pattern used

This problem follows a Simulation pattern.

1. Use a variable i = 1 to represent the current second and the amount of memory to allocate.
2. While memory1 >= i or memory2 >= i:
   • If memory1 >= memory2, subtract i from memory1.
   • Else, subtract i from memory2.
   • Increment i.
3. Return [i, memory1, memory2].

Example explanation

memory1 = 2, memory2 = 2

1. Second 1: memory1 (2) $\ge$ memory2 (2). memory1 = 2 - 1 = 1.
2. Second 2: memory1 (1) < 2 and memory2 (2) $\ge$ 2. memory2 = 2 - 2 = 0.
3. Second 3: Both sticks have $< 3$. Stop. Result: [3, 1, 0].

Common mistakes candidates make

• Tie-breaking Error: Subtracting from the wrong stick when memory1 == memory2.
• Loop condition: Stopping the loop if one stick fails, instead of only when both fail to meet the requirement.
• Return value: Forgetting that the "crash time" is the first second the allocation fails, not the last successful second.

Interview preparation tip

In simulation problems, dry-run your code with a small example. Pay close attention to the "equal" condition and the loop termination criteria. Being precise with word-for-word rule implementation is key.