使用sys.stdin解决蜗牛爬墙问题的技术咨询

Problem Overview #

• Input: Non-negative integers n (daily climb units), m (daily slip units), H (target height)
• Objective: Calculate the number of days required for the snail to reach or exceed the target height H
• Core Rules:
  • Each day starts with the snail climbing n units. If this takes it to H or higher, the day counts and no slip occurs.
  • If the climb doesn't reach H, the snail slips m units overnight (cannot go below ground level, i.e., 0).

Example Breakdowns #

• Example 1: Input 3 2 11 → Output 9
  • After 8 full days of climbing and slipping, the snail is at 8 units. On day 9, it climbs 3 units to reach 11, which meets the target.
• Example 2: Input 5 2 9 → Output 3
  • Day 1: Climb to 5, slip to 3. Day 2: Climb to 8, slip to 6. Day3: Climb to 11 (≥9), so the day counts as the final day.

Solution Code #

import sys

for line in sys.stdin:
    tokens = line.strip().split()
    if len(tokens) != 3:
        continue  # Skip lines with invalid input
    
    n = int(tokens[0])
    m = int(tokens[1])
    H = int(tokens[2])
    
    if H == 0:
        print(0)
        continue
    
    # Handle impossible cases
    if n == 0 or (n <= m and H > n):
        print("Impossible")
        continue
    
    days = 0
    current_height = 0
    
    while True:
        days += 1
        current_height += n
        
        if current_height >= H:
            print(days)
            break
        
        # Ensure snail doesn't slip below ground
        current_height = max(current_height - m, 0)

Using sys.stdin in VS Code #

• Running the Program:
  1. Open your Python file in VS Code.
  2. Press F5 or click the "Run" button to launch the program. The integrated terminal will open automatically.
• Testing with Manual Input:
  • Type your input line (e.g., 3 2 11) into the terminal and press Enter. The program will process the input and print the result.
  • For multiple test cases, enter each input line sequentially.
• Stopping the Program: Press Ctrl + C in the terminal to terminate the program.
• Using a Test File:
  1. Create a text file (e.g., test_input.txt) with one test case per line.
  2. In the terminal, run python your_script_name.py < test_input.txt to read input directly from the file.

Key Edge Cases Handled #

• If H = 0: The snail is already at the target, so days needed is 0.
• If n = 0 and H > 0: The snail can't climb, so output "Impossible".
• If n <= m and H > n: The snail can never reach the target (net gain per cycle is ≤0), so output "Impossible".
• If n >= H: The snail reaches the target on day 1.

内容的提问来源于stack exchange，提问作者Anon