Broken Calculator — LeetCode 991 Python Solution

The problem

There is a broken calculator that has the integer startValue on its display initially. In one operation, you can: multiply the number on display by 2, or subtract 1 from the number on display.

Example

Input

startValue = 2, target = 3

Output

2

Explanation

Use double operation and then decrement operation {2 -> 4 -> 3}.

Python solution

class Solution:
    def brokenCalc(self, startValue: int, target: int) -> int:
        ans = 0
        while startValue < target:
            if target & 1:
                target += 1
            else:
                target >>= 1
            ans += 1
        ans += startValue - target
        return ans

Complexity

Pattern: Greedy

Take the locally best option every time — when you can prove that never costs you later. LeetCode 991. Broken Calculator is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Greedy.

The greedy guide has the Python template for the pattern and the 346 LeetCode problems that use it.

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