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CycleSort.js
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59 lines (54 loc) · 1.61 KB
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/**
* Cycle sort is an in-place, unstable sorting algorithm,
* a comparison sort that is theoretically optimal in terms of the total
* number of writes to the original array, unlike any other in-place sorting
* algorithm. It is based on the idea that the permutation to be sorted can
* be factored into cycles, which can individually be rotated to give a sorted result.
*
* Wikipedia: https://en.wikipedia.org/wiki/Cycle_sort
*/
/**
* cycleSort takes an input array of numbers and returns the array sorted in increasing order.
*
* @param {number[]} list An array of numbers to be sorted.
* @return {number[]} An array of numbers sorted in increasing order.
*/
function cycleSort(list) {
for (let cycleStart = 0; cycleStart < list.length; cycleStart++) {
let value = list[cycleStart]
let position = cycleStart
// search position
for (let i = cycleStart + 1; i < list.length; i++) {
if (list[i] < value) {
position++
}
}
// if it is the same, continue
if (position === cycleStart) {
continue
}
while (value === list[position]) {
position++
}
const oldValue = list[position]
list[position] = value
value = oldValue
// rotate the rest
while (position !== cycleStart) {
position = cycleStart
for (let i = cycleStart + 1; i < list.length; i++) {
if (list[i] < value) {
position++
}
}
while (value === list[position]) {
position++
}
const oldValueCycle = list[position]
list[position] = value
value = oldValueCycle
}
}
return list
}
export { cycleSort }