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991. Broken Calculator

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

• Java
• C++
• Python
• Go

• 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;
      }
  };
  

• 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
  
  

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

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