Find Duplicate Array within Array

Question

Given an array of arrays, what would be the efficient way of identifying the duplicate item?

var array = [
  [
    11.31866455078125,
    44.53836644772605
          


        

Answer 1

You can just use plain javascript to do that, it's not that hard, here is my implementation

for (let i = 0; i < array.length; i++) {
  for (let j = i + 1; j < array.length; j++) {
  
     // quick elimination by comparing sub-array lengths
     if (array[i].length !== array[j].length) {
        continue;
     }
     // look for dupes
     var dupe = true;
     for (var k = 0; k < array[i].length; k++) {
       if (array[i][k] !== array[j][k]) {
         dupe = false;
         break;
       }
     }
     // if a dupe then print
     if (dupe) {
         console.debug("%d is a dupe", j); 
     }
   }
 }

The nice part about this implementation is that it will print you multiple times that an array at an index is a dupe for multiple dupes, you can use that fact to count your dupes in each index!

This is actually a very efficient way to do this because the inner for loop (j) always runs from the next position of the outer loop (i). so you half your check count.

And here is a plunk