Virus Spread (Intuit India)

Problem Overview

• Find the minimum seconds for a virus to infect all cells in an N×M grid, or return -1 if some stay uninfected.
• Input: N, M, and a matrix with 0 (empty), 1 (healthy), 2 (virus); Output: integer time or -1; Constraints: 1≤N,M≤100.
• Infection spreads each second to up, down, left, and right neighbors only.
• Real-world context: simulates virus spread in a petri dish.
• Asked in Intuit India interviews; a classic coding interview problem and interview question.