Question

How to find the first repeating element in an array of integers with JavaScript

Answer 1

function get_first_repeating_element(arr) {
    let min = -1;
 
    let set = new Set();
 
    for (let i = arr.length - 1; i >= 0; i--) {
        if (set.has(arr[i]))
            min = i;
        else 
            set.add(arr[i]);
    }
 
    if (min != -1)
        return arr[min];
    else
        return -1;
}

const arr = [ 1, 2, 4, 5, 6, 5, 4, 3, 7 ];

console.log(get_first_repeating_element(arr));


  
  
  
  
/*
run:
  
4
  
*/

 

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