equal.js

// source: https://www.hackerrank.com/challenges/equal/problem
// video: https://youtu.be/Mbfs-4URYmg
function equal(arr) {
    let rounds = Infinity
    const min = Math.min(...arr)
    // Go through each target value (min, min-1, min-2, ..., min-4)
    for (let n = 0; n < 5; n++){ // O(5) = O(1)
        const target = min - n
        let operationCount = 0
        // Go through each value in arr...
        for (const val of arr){ // O(n)
            // calculate difference b/t val and target
            const diff = val - target
            // use modular math and add to operationCount
            const fiveCount = Math.floor(diff / 5)
            const twoCount = Math.floor((diff % 5) / 2)
            const oneCount = (diff % 5) % 2
            operationCount += fiveCount + twoCount + oneCount
        }
        rounds = Math.min(rounds, operationCount)
    }
    return rounds // Time Complexity = O(n)
}