🎯 Guess Number Higher or Lower – Python (Binary Search)

Hi All,

Today I solved a fun and important problem: Guess Number Higher or Lower using Binary Search.

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📌 Problem Statement

We are given a number range from 1 to n.

👉 A number is already picked (hidden), and we need to guess it.

We use a predefined function:

guess(num)

It returns:

• -1 → Your guess is too high
• 1 → Your guess is too low
• 0 → Correct guess

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💡 Approach

🔹 Binary Search (Optimal)

👉 Idea:

• Search in the range [1, n]
• Use middle element
• Reduce search space based on result

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🧠 Step-by-Step Logic

1. Set:

   • low = 1
   • high = n

2. Find middle:
   

   mid = (low + high) // 2

1. Call guess(mid):
   • If 0 → return mid
   • If -1 → search left (high = mid - 1)
   • If 1 → search right (low = mid + 1)

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💻 Python Code

class Solution:
    def guessNumber(self, n):
        low = 1
        high = n

        while low <= high:
            mid = (low + high) // 2
            result = guess(mid)

            if result == 0:
                return mid
            elif result == -1:
                high = mid - 1
            else:
                low = mid + 1

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🔍 Example Walkthrough

Input:

n = 10
pick = 6

Steps:

• mid = 5 → guess(5) = 1 → go right
• mid = 8 → guess(8) = -1 → go left
• mid = 6 → guess(6) = 0 → found

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🖥️ Sample Output

Input: n = 10, pick = 6
Output: 6

Input: n = 1, pick = 1
Output: 1

Input: n = 2, pick = 1
Output: 1

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⚡ Complexity Analysis

• Time Complexity: O(log n) ✅
• Space Complexity: O(1) ✅

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🧠 Why this is important?

• Classic Binary Search problem
• Reduces search space efficiently
• Very common in interviews

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✅ Conclusion

This problem helped me understand:

• Binary search logic
• Efficient searching
• Problem-solving using API-based hints

🚀 A must-know problem for beginners!

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