【Java】几种面试常考排序

/**
* Created by sirius on 16/5/28.
*/

public class test {
public static void main(String[] args) {
int arr[] = {1,4,2,3,5,7,9,8,6};
//BetterBubbleSort(arr);
int len = arr.length;

//MergeSort(arr, 0, len-1);
//QuickSort(arr, 0, len-1);
InsertSort(arr);
for (int i = 0; i < arr.length; i++) {
System.out.println(arr[i]);
}
}

public static void InsertSort(int arr[]) {
int len = arr.length;

}

public static void QuickSort(int arr[], int left, int right) {
int index;
if (left < right) {
index = partition(arr, left, right);
QuickSort(arr, left, index -1);
QuickSort(arr, index + 1, right);
}
}

public static int partition(int arr[], int left, int right) {
int pivot = arr[left];
int i = left;
int j = right;
while (i < j) {
while (i < j && arr[j] >= pivot) {
j--;
}
if (i < j) {
arr[i++] = arr[j];
}
while (i < j && arr[i] <= pivot) {
i++;
}
if (i<j) {
arr[j--] = arr[i];
}
}
arr[i] = pivot;
return i;
}

public static void MergeSort(int arr[], int left , int right) {
if (left < right) {
int mid = ((right - left) >> 1) + left;
MergeSort(arr, left, mid);
MergeSort(arr, mid+1, right);
MergeArray(arr, left, mid, right);
}
}

public static void MergeArray(int arr[], int left, int mid, int right) {
int i = left;
int j = mid + 1;
int k = 0;
int[] tmp = new int[right - left + 1];
System.out.println("this time, left = " + left + ",right = " + right + ",i = " + i + ",j = " + j);

while (i <= mid && j <= right) {
if (arr[i] < arr[j]) {
tmp[k++] = arr[i++];
} else {
tmp[k++] = arr[j++];
}
}

while (i <= mid) {
tmp[k++] = arr[i++];
}

while (j <= right) {
tmp[k++] = arr[j++];
}

for (int k2 = 0; k2 < tmp.length; k2++) {
arr[k2 + left] = tmp[k2];
}
}

public static void BubbleSort(int arr[]) {
int len = arr.length;
for (int i = 0; i < len; i++) {
for (int j = 1; j < len - i; j++) {
if (arr[j-1] > arr[j]) {
int tmp = arr[j-1];
arr[j-1] = arr[j];
arr[j] = tmp;
}
}
}
}

public static void BetterBubbleSort(int arr[]) {
//如果这一趟没有发生交换,说明排序已经完成
int len = arr.length;
boolean flag = true;
for (int i = 0; i < len && flag; i++) {
flag = false;
for (int j = 1; j < len - i; j++) {
//如果一次都没有交换,那么flag = false,就可以跳出了
if (arr[j-1] > arr[j]) {
int tmp = arr[j-1];
arr[j-1] = arr[j];
arr[j] = tmp;
flag = true;
}
}
}
}

}