Number of Ways to Divide a Long Corridor LeetCode solution in Rust

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impl Solution {
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  pub fn number_of_ways(corridor: String) -> i32 {
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    const MOD: u64 = (1e9 + 7.) as _;
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    let mut count = 1;
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    let mut seats = 0;
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    let mut j = None;
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    for (i, c) in corridor.char_indices() {
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      if c == 'S' {
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        seats += 1;
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        if seats == 2 {
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          j = Some(i);
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          seats = 0;
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        } else if seats == 1 && j.is_some() {
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          count = (count * (i - j.unwrap()) as u64) % MOD;
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        }
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      }
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    }
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    if seats == 1 || j.is_none() {
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      return 0;
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    }
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    count as _
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  }
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}