Finding first unique element in sorted array in JavaScript

Suppose, we have a sorted array of literals like this −

const arr = [32, 32, 63, 63, 63, 75, 75, 86, 87, 88, 89];

We are required to write a JavaScript function that takes in one such array and returns the first unique number in the array.

If there is no such number in the array, our function should return false.

For this array, the output should be 86.

The code for this will be −

const arr = [32, 32, 63, 63, 63, 75, 75, 86, 87, 88, 89];
const firstUnique = arr => {
   let appeared = false;
   for(let i = 0; i < arr.length; i++){
      if(appeared){
         if(arr[i+1] !== arr[i]){
            appeared = false;
         };
      }else{
         if(arr[i+1] === arr[i]){
            appeared = true;
            continue;
         };
         return arr[i];
      };
   };
   return false;
};
console.log(firstUnique(arr));

Following is the output on console −

86

AmitDiwan

Updated on: 09-Oct-2020

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