0991-broken-calculator

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Description

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.

Given two integers startValue and target, return the minimum number of operations needed to display target on the calculator.

 

Example 1:

Input: startValue = 2, target = 3
Output: 2
Explanation: Use double operation and then decrement operation {2 -> 4 -> 3}.

Example 2:

Input: startValue = 5, target = 8
Output: 2
Explanation: Use decrement and then double {5 -> 4 -> 8}.

Example 3:

Input: startValue = 3, target = 10
Output: 3
Explanation: Use double, decrement and double {3 -> 6 -> 5 -> 10}.

 

Constraints:

• 1 <= startValue, target <= 109

Solution(Python)

class Solution:
    def brokenCalc(self, startValue: int, target: int) -> int:
        cnt = 0
        while target > startValue:
            if startValue == target:
                break
            if not target % 2:
                target//=2
            else:
                target+=1
            cnt+=1

        return cnt + startValue -target