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impl Solution {
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  pub fn reverse(x: i32) -> i32 {
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    let mut x = x;
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    let mut ret: i32 = 0;
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    while x != 0 {
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      let d: i32 = x % 10;
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      x = x / 10;
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      match ret.checked_mul(10).and_then(|val| val.checked_add(d)) {
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        Some(val) => ret = val,
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        None => return 0,
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      }
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    }
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    ret
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  }
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}