Question

991. Broken Calculator

中文文档

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

Solutions

Solution 1

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

class Solution {
  public int brokenCalc(int startValue, int target) {
    int ans = 0;
    while (startValue < target) {
      if ((target & 1) == 1) {
        target++;
      } else {
        target >>= 1;
      }
      ans += 1;
    }
    ans += startValue - target;
    return ans;
  }
}

class Solution {
public:
  int brokenCalc(int startValue, int target) {
    int ans = 0;
    while (startValue < target) {
      if (target & 1) {
        target++;
      } else {
        target >>= 1;
      }
      ++ans;
    }
    ans += startValue - target;
    return ans;
  }
};

func brokenCalc(startValue int, target int) (ans int) {
  for startValue < target {
    if target&1 == 1 {
      target++
    } else {
      target >>= 1
    }
    ans++
  }
  ans += startValue - target
  return
}