On a broken calculator that has a number showing on its display, we can perform two operations:
- Double: Multiply the number on the display by 2, or;
- Decrement: Subtract 1 from the number on the display.
Initially, the calculator is displaying the number X.
Return the minimum number of operations needed to display the number Y.
Example 1:
Input: X = 2, Y = 3
Output: 2
Explanation: Use double operation and then decrement operation {2 -> 4 -> 3}.
Example 2:
Input: X = 5, Y = 8
Output: 2
Explanation: Use decrement and then double {5 -> 4 -> 8}.
Example 3:
Input: X = 3, Y = 10
Output: 3
Explanation: Use double, decrement and double {3 -> 6 -> 5 -> 10}.
Example 4:
Input: X = 1024, Y = 1 Output: 1023 Explanation: Use decrement operations 1023 times.
Note:
1 <= X <= 10^91 <= Y <= 10^9
在显示着数字的坏计算器上，我们可以执行以下两种操作：
- 双倍（Double）：将显示屏上的数字乘 2；
- 递减（Decrement）：将显示屏上的数字减 1 。
最初，计算器显示数字 X。
返回显示数字 Y 所需的最小操作数。
示例 1：
输入：X = 2, Y = 3
输出：2
解释：先进行双倍运算，然后再进行递减运算 {2 -> 4 -> 3}.
示例 2：
输入：X = 5, Y = 8
输出：2
解释：先递减，再双倍 {5 -> 4 -> 8}.
示例 3：
输入：X = 3, Y = 10
输出：3
解释：先双倍，然后递减，再双倍 {3 -> 6 -> 5 -> 10}.
示例 4：
输入：X = 1024, Y = 1 输出：1023 解释：执行递减运算 1023 次
提示：
1 <= X <= 10^91 <= Y <= 10^9
Runtime: 8 ms
Memory Usage: 3.9 MB
1 class Solution {
2 func brokenCalc(_ X: Int, _ Y: Int) -> Int {
3 var ret:Int = Int.max
4 for d in 0...30
5 {
6 var t = (X<<d) - Y
7 if t < 0 {continue}
8 var num:Int = d
9 for e in 0..<d
10 {
11 num += t&1
12 t >>= 1;
13 }
14 num += t
15 ret = min(ret, num)
16 }
17 return ret
18 }
19 }