algos/commonElement.js at main · davidmichaelmackey/algos · GitHub

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// Write code to create a function that accepts two arrays of numbers
// There will be one number common to both arrays
// Return the common number
// You may not use the `indexOf` or `includes` method

var commonElement = function(arrA, arrB) {
  var elements = {};

  for (var i = 0; i < arrA.length; i++) {
    var num = arrA[i];
    elements[num] = true;
  }

  for (var i = 0; i < arrB.length; i++) {
    var num = arrB[i];

    if (elements[num] === true) {
      return num;
    }
  }
};

// This could also be achieved using a Set data structure

// var commonElement = function(arrA, arrB) {
//   var elements = new Set();

//   for (var i = 0; i < arrA.length; i++) {
//     var num = arrA[i];
//     elements.add(num);
//   }

//   for (var i = 0; i < arrB.length; i++) {
//     var num = arrB[i];

//     if (elements.has(num)) {
//       return num;
//     }
//   }
// };