BeautifulArrays

function solve(arr) {
    let sorted = arr.slice().sort((a, b) => a - b);
    let swapsAsc = findSwaps(arr, sorted);
    let swapsDesc = findSwaps(arr, sorted.slice().reverse());
    return Math.min(swapsAsc, swapsDesc);
}

function findSwaps(arr, sorted) {
    // map value to index
    let value2index = arr.reduce((acc, curr, index) => {acc[curr] = index; return acc}, {});
    let answer = 0;
    for (let i = 0; i < arr.length; i++) {
        // At index i there must be value sorted[i]
        if (arr[i] != sorted[i]) {
            // Find the position of value sorted[i] in the input array
            let position = value2index[sorted[i]];
            // Swap sorted[i] with a[i]
            let temp = arr[i];
            arr[i] = arr[position];
            arr[position] = temp;
            // Update the position of a[position] in the value2index map
            value2index[arr[position]] = position;
            // Increment swap count
            answer++;
        }
    }
    return answer;
}

console.log(solve([2, 5, 3, 1])); // should return 2