Quick Sort

Approach #1 Iterative - Select the middle index as Pivot

class Solution {
public void quickSort(int[] arr, int low, int high) {
if (arr == null || arr.length == 0) return;
if (low >= high) return;
int middle = low + (high - low) / 2;
int pivot = arr[middle];
int i = low, j = high;
while (i <= j) {
while (arr[i] < pivot) {
i++;
}
while (arr[j] > pivot) {
j--;
}
if (i <= j) {
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
i++;
j--;
}
}
if (low < j) {
quickSort(arr, low, j);
}
if (high > i) {
quickSort(arr, i, high);
}
}
}

Approach #2 Select the last value of the array as Pivot

class Solution {
public void quickSort(int[] arr, int start, int end) {
int partition = partition(arr, start, end);
if (start < partition - 1) {
quickSort(arr, start, partition - 1);
}
if (partition + 1 < end) {
quickSort(arr, partition + 1, end);
}
}
public int partition(int[] arr, int start, int end) {
int pivot = arr[end];
for (int i = start; i < end; i++) {
if (arr[i] < pivot) {
swap(arr, start, i);
start++;
}
}
swap(arr, start, end);
return start;
}
private void swap(int[] arr, i, j) {
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
Last modified 2yr ago