数组相关算法:冒泡、二分法、快排
文章目录
冒泡排序
public static void main(String[] args) {
int[] arr = new int[]{43,32,76,-98,0,64,33,-21,32,99};
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 temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
}
}
}
}
二分法查找
前提:所要查找的数组必须有序。
int[] arr = new int[]{-98, -34, 2, 34, 54, 66, 79, 105, 210, 333};
int dest = 34;//要查找的数字
int head = 0;//初始的首索引
int end = arr.length - 1;//初始的末索引
boolean isFlag = true;
while (head <= end) {
int middle = (head + end) / 2;
if (dest == arr[middle]) {
System.out.println("找到了指定的元素,下标为:" + middle);
isFlag = false;
break;
} else if (arr[middle] > dest) {
end = middle - 1;
} else {//arr2[middle] < dest
head = middle + 1;
}
}
if (isFlag) {
System.out.println("很遗憾,没有找到!");
}
快速排序算法
通过一趟排序将待排序记录分割成独立的两部分,其中一部分记录的关键字均比另一部分关键字小,则分别对这两部分继续进行排序,直到整个序列有序。
public class QuickSort {
private static void swap(int[] data, int i, int j) {
int temp = data[i];
data[i] = data[j];
data[j] = temp;
}
private static void subSort(int[] data, int start, int end) {
if (start < end) {
int base = data[start];
int low = start;
int high = end + 1;
while (true) {
while (low < end && data[++low] - base <= 0)
;
while (high > start && data[--high] - base >= 0)
;
if (low < high) {
swap(data, low, high);
} else {
break;
}
}
swap(data, start, high);
subSort(data, start, high - 1);//递归调用
subSort(data, high + 1, end);
}
}
public static void quickSort(int[] data) {
subSort(data, 0, data.length - 1);
}
public static void main(String[] args) {
int[] data = {9, -16, 30, 23, -30, -49, 25, 21, 30};
System.out.println("排序之前:\n" + java.util.Arrays.toString(data));
quickSort(data);
System.out.println("排序之后:\n" + java.util.Arrays.toString(data));
}
}