Python猜数字游戏二分查找范围更新错误求助

Hey there! Let's work through the issues in your binary search logic and get this number guesser working right.

What's Going Wrong #

Your current code breaks the binary search range because you're updating low and high with incorrect calculations:

• When the user says the guess is too high ('h'), you set high = ans//2—this chops the range way down instead of just setting the upper bound to your current guess (since the secret number must be smaller than ans).
• When the guess is too low ('l'), low = ans*2 jumps the range back up, completely abandoning the narrow search you started.
• The win condition check_ans == 'c' and check_ans == user_num is also flawed: check_ans is a string, and user_num is an integer—they'll never match. You just need to trust the user's 'c' input means you guessed right.

Fixed Code #

Here's the corrected version with proper binary search behavior:

user_num = int(input("Please think of a number between 0 and 100! "))
low = 0
high = 100
ans = (high + low) // 2

while True:
    print(f"Is your secret number {ans}?")
    check_ans = input("Enter 'h' if the guess is too high, 'l' if too low, 'c' if correct: ").lower()
    
    if check_ans == 'h':
        # Guess was too high—new upper bound is current answer
        high = ans
        ans = (low + high) // 2
    elif check_ans == 'l':
        # Guess was too low—new lower bound is current answer
        low = ans
        ans = (low + high) // 2
    elif check_ans == 'c':
        print(f"Game over. Your secret number was: {ans}")
        break
    else:
        print("I don't understand your command. Please try again.")

Key Fixes Explained #

1. Proper Range Updates:
   • For 'h': Set high = ans (since the secret number is smaller than your guess) then recalculate ans as the midpoint of the new low and high.
   • For 'l': Set low = ans (since the secret number is larger than your guess) then recalculate the midpoint.
2. Simplified Win Condition: Just check for 'c'—the user will only input this when you've guessed correctly.
3. Robust Input Handling: Added .lower() so the program accepts uppercase inputs like 'H' or 'L' too.
4. Cleaner String Formatting: Used f-strings instead of concatenation for readability.

Testing with 34 #

Let's walk through your test case (secret number 34):

1. Initial guess: (0+100)//2 = 50 → user inputs 'h'
2. New high = 50, guess becomes (0+50)//2 =25 → user inputs 'l'
3. New low=25, guess becomes (25+50)//2=37 → user inputs 'h'
4. New high=37, guess becomes (25+37)//2=31 → user inputs 'l'
5. New low=31, guess becomes (31+37)//2=34 → user inputs 'c'
6. Game ends correctly!

内容的提问来源于stack exchange，提问作者FanonX Rogers