Data Structures · Question 15 · Hard
Data Structures question 15
Two stacks share a single array arr[0..n-1]. Stack 1 starts at index 0 and grows right (top1 starts at -1); stack 2 starts at index n-1 and grows left (top2 starts at n). When does a push to either stack overflow?
- When top1 == n / 2
- When top1 + 1 == top2
- When top2 == 0
- When top1 == top2
Answer and explanation
Answer: B. When top1 + 1 == top2
Explanation: The stacks grow toward each other and can use any free slot. The array is full only when no gap is left between them, i.e. top1 + 1 == top2. Splitting at n / 2 would waste space.
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