Number of Equivalent Domino Pairs LeetCode solution in Rust

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use std::collections::HashMap;
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impl Solution {
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  pub fn num_equiv_domino_pairs(dominoes: Vec<Vec<i32>>) -> i32 {
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    let mut count = HashMap::new();
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    for d in dominoes {
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      let d = (d[0].min(d[1]), d[0].max(d[1]));
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      *count.entry(d).or_insert(0) += 1;
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    }
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    count.values().map(|c| (c * (c - 1)) / 2).sum()
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  }
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}