Question

How to find an element that appears once in an array of elements that appears three times in JavaScript

Answer 1

const findElementThatAppearsOnceInArray = (arr) => {
    const map = new Map();

    for (const x of arr) {
        map.set(x, (map.get(x) || 0) + 1);
    }

    for (const [key, value] of map) {
        if (value === 1) {
            return key;
        }
    }

    return -1;
};

const arr = [3, 5, 5, 2, 7, 3, 2, 8, 8, 3, 2, 5, 8];

console.log(findElementThatAppearsOnceInArray(arr));



/*
run:

7

*/

 

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