Java basic sorting example tutorial

Record several java sorting codes that I compiled

public class Index {

public static void main(String[] args) {

int[] a = { 1, 4, 5, 6, 8, 2, 3, 9, 6, };
// selectSort(a);
// bubbleSort(a);
// insertSort(a);
// quickSort(a, 0, a.length - 1);
// quickSort(a, 0, a.length - 1);
shellSort(a) ;
for (int b : a) {
System.out.println(b);
}

}

// select sort, from the following list Select the largest one and put it in front
public static void selectSort(int[] arr) {

for (int i = 0; i < arr.length - 1; i++) {

for (int j = i + 1; j < arr.length; j++) {

if (arr[i] < arr[j]) {
int tem = arr[ j];
arr[j] = arr[i];
arr[i] = tem;
}

}
}

}

// bubble sort, in the sub-loop, compare and exchange pairs, like bubbling, so that large numbers are placed at the back
public static void bubbleSort(int[] arr) {

for (int i = 0; i < arr.length - 1; i++) {

for (int j = 0; j < arr.length - 1 - i; j++) {

if (arr[j] > arr[j + 1]) {
int tem = arr[j + 1];
arr[j + 1] = arr[j];
arr [j] = tem;
}
}

}

}

// insert sort, assuming that the previous ones are in order, in the sub-loop , compare the target element with the previous one, move forward when encountering a larger one, insert it at that position when encountering a smaller one
public static void insertSort(int[] arr) {

for (int i = 1; i < arr.length; i++) {

int j = i;
int temp = arr[i];
while (j > 0) {
if (temp < arr[j - 1]) {

arr[j] = arr[j - 1];

arr[j - 1] = temp;
}
j--;

}

}

}

// quick sort, similar to the idea of ​​​​half, let the left side of a certain value Less than it, the one on the right is greater than it, and then recurse on both sides
public static void quickSort(int[] arr, int low, int high) {
int start = low;
int end = high;
int key = arr[start];

while (end > start) {

while (end > start && arr[end] >= key) {
end --;
}
if (arr[end] <= key) {
int tem = arr[end];
arr[end] = arr[start];
arr [start] = tem;
}
while (start < end && arr[start] <= key) {
start++;
}
if (arr[start] > = key) {
int tem = arr[start];
arr[start] = arr[end];
arr[end] = tem;
}

}

if (start > low) {
quickSort(arr, low, start - 1);

}
if (end < high) {
quickSort( arr, end + 1, high);
}

}

// shell sort, similar to selection sort, but with increment, the idea of ​​​​first coarse and then fine (first Sort roughly, then sort carefully)
public static void shellSort(int[] arr) {
int d = arr.length / 2;

while (d >= 1) {
for (int i = 0; i < arr.length; i++) {
for (int j = i; j < arr.length - d; j = j + d) {
if (arr [j] > arr[j + d]) {
int tem = arr[j];
arr[j] = arr[j + d];
arr[j + d] = tem ;
}
}
}
d = d / 2;

}
}

}

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