mostFreqK.js

const a = [4,4,0,0,2,3,1,2,2]

let i = 0
let mostFreqK = 0

while (i < a.length) {
	if (a[i] < 0) {
		i++
		continue
	}
	const k = a[i]
	if (a[k] > -1) {
		[a[i], a[k]] = [a[k], a[i]]
		a[k] = -2
	} else {
		if (k != i) {
			a[i] = -1
		}
		a[k] -= 1
		if (a[mostFreqK] > a[k]) mostFreqK = k
	}
}