冒泡排序
private static void bubbleSort(int[] arr) {
if (arr == null || arr.length < 2) {
return;
}
for (int end = arr.length - 1; end > 0; end--) {
for (int i = 0; i < end; i++) {
if(arr[i] > arr[i + 1]) {
swap(arr, i, i + 1);
}
}
}
}
选择排序
private static void selectSort(int[] arr) {
if (arr == null || arr.length < 2) {
return;
}
for (int i = 0; i < arr.length - 1; i++) {
int minIndex = i;
for (int j = i + 1; j < arr.length; j++) {
minIndex = arr[j] > arr[minIndex] ? minIndex : j;
}
swap(arr, i, minIndex);
}
}
插入排序
private static void insertionSort(int[] arr) {
if (arr == null || arr.length < 2) {
return;
}
for (int i = 1; i < arr.length; i++) {
int j = i - 1;
while (j >= 0 && arr[j] > arr[j + 1]) {
swap(arr, j, j + 1);
j--;
}
}
}
归并排序
private static void mergeSort(int[] arr) {
if (arr == null || arr.length < 2) {
return;
}
mergeSort(arr, 0, arr.length - 1);
}
private static void mergeSort(int[] arr, int l, int r) {
if (l == r) {
return;
}
int mid = l + (r - l) / 2;
mergeSort(arr, l, mid);
mergeSort(arr, mid + 1, r);
merge(arr, l, mid, r);
}
private static void merge(int[] arr, int l, int mid, int r) {
int[] help = new int[r - l + 1];
int p1 = l, p2 = mid + 1;
int i = 0;
while (p1 <= mid && p2 <= r) {
help[i++] = arr[p1] < arr[p2] ? arr[p1++] : arr[p2++];
}
while (p1 <= mid) {
help[i++] = arr[p1++];
}
while (p2 <= r) {
help[i++] = arr[p2++];
}
for (i= 0; i < help.length; i++) {
arr[l + i] = help[i];
}
}
荷兰国旗
public class NetherlandsFlag {
public static void main(String[] args) {
int[] arr = {2,3,5,3,3,6,9,8,4,5,5,5};
int[] sameArr = partition(arr, 0, arr.length - 1, 5);
System.out.println(Arrays.toString(sameArr));
System.out.println(Arrays.toString(arr));
}
private static int[] partition(int[] arr, int L, int R, int num) {
int less = L - 1;
int more = R + 1;
int cur = L;
while (cur < more) {
if (arr[cur] < num) {
swap(arr, ++less, cur++);
} else if (arr[cur] > num) {
swap(arr, --more, cur);
} else {
cur++;
}
}
return new int[]{less + 1, more - 1};
}
private static void swap(int[] arr, int i, int j) {
int tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
}
快速排序
public static void main(String[] args) {
int[] arr = {4,5,2,2,6,9,10};
quickSort(arr);
System.out.println(Arrays.toString(arr));
}
private static void quickSort(int[] arr) {
quickSort(arr, 0, arr.length - 1);
}
private static void quickSort(int[] arr, int left, int right) {
if (left < right) {
int pos = partition(arr, left, right);
quickSort(arr, left, pos - 1);
quickSort(arr, pos + 1, right);
}
}
private static int partition(int[] arr, int left, int right) {
int pivot = arr[left];
int i = left, 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 main(String[] args) {
int[] arr = {4,5,2,2,6,9,10};
quickSort(arr);
System.out.println(Arrays.toString(arr));
}
private static void quickSort(int[] arr) {
if (arr == null || arr.length < 2) {
return;
}
quickSort(arr, 0, arr.length - 1);
}
private static void quickSort(int[] arr, int l, int r) {
if (l < r) {
swap(arr, l + (int) Math.random() * (r - l + 1), r);
int[] pos = partition(arr, l, r);
quickSort(arr, l, pos[0] - 1);
quickSort(arr, pos[1] + 1, r);
}
}
private static int[] partition(int[] arr, int l, int r) {
int less = l - 1;
int more = r + 1;
while (l < more) {
if (arr[l] < arr[r]) {
swap(arr, ++less, l++);
} else if (arr[l] > arr[r]) {
swap(arr, --more, l);
} else {
l++;
}
}
return new int[]{less + 1, more - 1};
}
private static void swap(int[] arr, int i, int j) {
int tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
堆排序
public static void main(String[] args) {
int[] arr = {5,2,1,4,3};
heapSort(arr);
System.out.println(Arrays.toString(arr));
}
private static void heapSort(int[] arr) {
int size = arr.length;
if (arr == null || size < 2) {
return;
}
for (int i = 0; i < size; i++) {
heapInsert(arr, i);
}
while (size > 1) {
swap(arr, 0, size - 1);
size--;
heapify(arr, 0, size);
}
}
private static void heapInsert(int[] arr, int index) {
while (arr[index] > arr[(index - 1) / 2]) {
swap(arr, index, (index - 1) / 2);
index = (index - 1) / 2;
}
}
private static void heapify(int[] arr, int index, int size) {
int left = 2 * index + 1;
while (left < size) {
int largestIndex = 0;
if (left + 1 < size && arr[left + 1] > arr[left]) {
largestIndex = left + 1;
} else {
largestIndex = left;
}
largestIndex = arr[index] > arr[largestIndex] ? index : largestIndex;
if (index == largestIndex) {
break;
}
swap(arr, index, largestIndex);
index = largestIndex;
left = 2 * index + 1;
}
}
private static void swap(int[] arr, int i, int j) {
int tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
Processed:
0.032, SQL:
9
