public static void quickSort(int[] data, int left, int right){
if(left < right){
int mid = getMid(data,left,right);
quickSort(data,left,mid-1);
quickSort(data,mid+1,right);
}
}
public static int getMid(int[] data,int left, int right){
int pivot = data[left];
while (left < right){
while(left < right && data[right] >= pivot){
right--;
}
data[left] = data[right];
while(left < right && data[left] <= pivot){
left++;
}
data[right] = data[left];
}
data[left] = pivot;
return left;
}
非遞歸
/**
* @param A an integer array
* @return void
*/
public void sortIntegers(int[] A) {
quickSort(A, 0, A.length - 1);
}
private void quickSort(int[] A, int start, int end) {
if (start >= end) {
return;
}
int left = start, right = end;
// key point 1: pivot is the value, not the index
int pivot = A[(start + end) / 2];
// key point 2: every time you compare left & right, it should be
// left <= right not left < right
while (left <= right) {
// key point 3: A[left] < pivot not A[left] <= pivot
while (left <= right && A[left] < pivot) {
left++;
}
// key point 3: A[right] > pivot not A[right] >= pivot
while (left <= right && A[right] > pivot) {
right--;
}
if (left <= right) {
int temp = A[left];
A[left] = A[right];
A[right] = temp;
left++;
right--;
}
}
quickSort(A, start, right);
quickSort(A, left, end);
}
