## 991. Broken Calculator

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

**Example 2:**

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

**Example 3:**

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

**Example 4:**

Input:X = 1024, Y = 1Output:1023Explanation:Use decrement operations 1023 times.

**Note:**

`1 <= X <= 10^9`

`1 <= Y <= 10^9`

## Rust Solution

```
struct Solution;
impl Solution {
fn broken_calc(x: i32, mut y: i32) -> i32 {
let mut res = 0;
while y > x {
if y % 2 == 0 {
y /= 2;
} else {
y += 1;
}
res += 1;
}
res + x - y
}
}
#[test]
fn test() {
let x = 2;
let y = 3;
let res = 2;
assert_eq!(Solution::broken_calc(x, y), res);
let x = 5;
let y = 8;
let res = 2;
assert_eq!(Solution::broken_calc(x, y), res);
let x = 3;
let y = 10;
let res = 3;
assert_eq!(Solution::broken_calc(x, y), res);
let x = 1024;
let y = 1;
let res = 1023;
assert_eq!(Solution::broken_calc(x, y), res);
}
```

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