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| class quick_sort {
/**
* 前后指针快排法
*/
public static void quickSortByTwoPointer(int[] a,int startIndex, int endIndex){
if (startIndex >= endIndex){
return;
}
int partitionIndex = getPartitionIndexByTwoPointer(a,startIndex,endIndex);
quickSortByTwoPointer(a, startIndex, partitionIndex-1);
quickSortByTwoPointer(a, partitionIndex + 1, endIndex);
}
private static int getPartitionIndexByTwoPointer(int[] a, int startIndex, int endIndex){
int left = startIndex;
int right = endIndex;
int pivot = a[startIndex];
while (left != right){
while (left < right && a[right] > pivot){
right --;
}
while (left < right && a[left] <= pivot){
left ++;
}
if (left < right){
a[left] = a[left] + a[right];
a[right] = a[left] - a[right];
a[left] = a[left] - a[right];
}
System.out.println("after replace "+Arrays.toString(a));
}
System.out.println("before change "+ Arrays.toString(a));
a[startIndex] = a[left];
a[left] = pivot;
System.out.println("after change "+Arrays.toString(a));
return left;
}
public static void quickSortByFillEmpty(int[] a, int startIndex, int endIndex){
if (startIndex > endIndex){
return;
}
int partitionIndex = getPartitionIndexByFillEmpty(a, startIndex,endIndex);
quickSortByFillEmpty(a, startIndex, partitionIndex-1);
quickSortByFillEmpty(a, partitionIndex +1, endIndex);
}
private static int getPartitionIndexByFillEmpty(int[] a, int startIndex, int endIndex){
int index = startIndex;
int left = startIndex;
int right = endIndex;
int pivot = a[startIndex];
while (left < right){
while (left < right){
if (a[right] < pivot){
a[index] = a[right];
index = right;
left ++;
break;
}
right --;
}
while (left < right){
if (a[left] > pivot){
a[index] = a[left];
index = left;
right --;
break;
}
left ++;
}
}
a[index] = pivot;
return index;
}
public static void main(String[] args) {
int[] a = new int[]{3,4,9,1,2,6,5,2,1};
System.out.println(Arrays.toString(a));
quickSortByTwoPointer(a,0, a.length-1);
System.out.println(Arrays.toString(a));
// int a = 1;
// int b = 2;
// a = a + b;
// b = a - b;
// a = a - b;
// System.out.println(a);
// System.out.println(b);
}
}
|