冒泡排序
//bubble sort
public static void bubbleSort(int[] array, int n){
int i = 0;// loop
int j = 0; // element index
while(i < n) {
for(j=0; j<n-i-1; j++){
if( array[j] > array[j+1] ){ //swap condition
swap( array, j, j +1 );
}
}
i++;
}
}
快速排序
//quick sort
public static void quickSort(int[] array, int lo, int hi){
if(lo>hi) return;
int pivot = array[lo];
int i = lo;
int j = hi;
while( i<j ){
//get smaller after pivot
//warning: while condition, here and next while
//at least one item is >=
while(i < j && array[j] >= pivot){
j--;
}
array[i] = array[j]; //so at j an element is void
//get bigger before pivot
while(i < j && array[i] < pivot){
i++;
}
array[j] = array[i]; // at i an element is to fill at j
}
//here, i bumps into j
array[i] = pivot;
//here, before index i smaller than pivot, after bigger than pivot
// lo~i quick sort
quickSort(array, lo, i-1);
// i+1~hi quick sort
quickSort(array, i+1, hi);
}
直接选择排序
//direct select sort
public static void selectSort(int[] array, int n){
int i=0; //sorted last element
int j=0; //unsorted first element
while(i<n){
int min=array[i];
int index = i;
for(j=i+1; j<n;j++){
if(array[j]<min){
min = array[j];
index = j;
}
}
swap(array,i,index);
i++;
}
}
堆排序
//heap sort
public static void heapSort(int[] array, int n){
for (int i = n / 2 - 1; i >= 0; i--)
buildHeap(array, n, i);
int len = n - 1;
while (len > 0) {
swap(array, 0, len);
buildHeap(array, len, 0);
len--;
}
}
private static void buildHeap(int[] array, int n, int i){
for (; left(i) < n; i = left(i)) {
int bigger =
right(i) < n ? max(array, left(i), right(i)) : left(i);
if (array[bigger] > array[i]) //swap
swap(array, bigger, i);
else break;
}
}
private static int left(int i){
return 2*i+1;
}
private static int right(int i){
return 2*i+2;
}
private static int max(int[] array, int i, int j){
return array[i]>array[j]? i:j;
}
直接插入排序
// insert sort
public static void insertSort(int[] array, int n){
int i = 1; //unsorted first index
while (i < n) {
int j = i - 1; //sorted last index
int insert = array[i]; //warning: label array[i]
while (j > 0 && insert < array[j]){
array[j + 1] = array[j];
j--;
}
array[j + 1] = insert; //j+1 is insert pos
i++;
}
}
希尔排序
//shell Sort
public static void shellSort(int[] array, int n, int group){
if (group > n) return;
int d = n / group; //d: number for each group
while (d > 0){
for (int i = 0; i < d; i++){
int j = i; // number index
int k = 1; //distance index
while (j < n){
int insert = array[j]; //label unsorted first
j -= d; //sorted last index
while (j > 0 && insert < array[j]){
array[j + d] = array[j];
j -= d;
}
array[j + d] = insert; //insert pos: j+d
j = i + (++k) * d; //next number index
}
}
d /= 2;
}
}
归并排序
//merge sort
public static void mergeSort(int[] array, int n){
var sorted = new int[n];
mergeSort(array,sorted,0,n-1);
}
private static void mergeSort(int[] array, int[] sorted, int lo, int hi){
if (lo < hi){
int mid = lo + (hi - lo) / 2;
mergeSort(array, sorted,lo, mid);
mergeSort(array, sorted, mid + 1, hi);
merge(array, sorted, lo, mid, hi);
}
}
//beg: part1 beginning index
//mid: part1 end index
//mid+1: part2 beginning index
//end: part2 end index
private static void merge(int[] array, int[] sorted, int beg, int mid, int end){
int i = beg; //part1 index
int j = mid + 1; //part2 index
int k = 0; //merged index
while (i <= mid && j <= end)
sorted[k++] =
array[i] <= array[j] ? array[i++] : array[j++];
while (i <= mid)
sorted[k++] = array[i++];
while (j <= end)
sorted[k++] = array[j++];
for (i = 0; i < k; i++)
array[beg + i] = sorted[i];
}
