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  1. Count Triplets
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Count Triplets

  • Matthew_Garneau
     + 0 comments

    This one was a doozy! Took me way longer then I'd care to admit. JS solution (forgive my nesting 😅):

    function countTriplets(arr, r) {
    let result = 0;
    
    const values = {};
    const pairs = {};
    
    for(const v of arr) {
      const prev = v/r;
      
      if(prev in values) {
        if (prev in pairs) result += pairs[prev];
        
        pairs[v] = (pairs[v] ?? 0) + values[prev];
      }
      
      values[v] = (values[v] ?? 0) + 1;
    }
    
    return result;
}