Java二分法查找数组元素

Array类：

package chapter5;import java.util.Random;public class Array {public static int[] generateArray() {System.out.println("generate Array... ");int[] group500;group500 = new int[10];System.out.println("generate Array successful... ");System.out.println("the Array length is: " + group500.length);return group500;}public static int[] generateArray(int length) {System.out.println("generate Array... ");int[] group500;group500 = new int[length];System.out.println("generate Array successful... ");System.out.println("the Array length is: " + group500.length);return group500;}public static int[] setSortDate(int[] array) {System.out.println("the Array is:");for (int i = 1; i <= array.length; i++) {array[i - 1] = i;System.out.print(array[i] + " ");}return array;}public static int[] setSortDate(int[] array, int[] arrayData) {System.out.println("the Array is:");for (int i = 0; i < array.length; i++) {array[i] = arrayData[i];System.out.print(array[i] + " ");}return array;}public static int[] setRadomDate(int[] array) {System.out.println("the Array is:");for (int i = 0; i < array.length; i++) {array[i] = new Random().nextInt(array.length) + 1;for (int j = 0; j < i + 1; j++) {if ((i != j) && array[i] == array[j])array[i] = new Random().nextInt(array.length) + 1;}}for (int i = 0; i < array.length; i++) {System.out.print(array[i] + " ");}return array;}public static void sort(int[] array) {System.out.println();System.out.println("now we will sort it as 1~9:");for (int i = 0; i < array.length; i++) {// int k;int tmp;// k = i;for (int j = i + 1; j < array.length; j++) {if (array[i] > array[j]) {tmp = array[i];array[i] = array[j];array[j] = tmp;}}}System.out.println("now the result is: ");for (int i = 0; i < array.length; i++) {System.out.print(array[i] + " ");}}public static String search(int[] array, int beSearchedNum) {// TODO Auto-generated method stubSystem.out.println();System.out.println(beSearchedNum + " wanted be search!");System.out.println("now we will search its index");int min = 0;int max = array.length - 1;int mid = (int) ((min + max) / 2);int searchTimes = 0;int searchTimesMax = array.length;String result = null;String sorry = "Sorry, the system can't find ur Num!";if (array[min] <= beSearchedNum && array[max] >= beSearchedNum) {while (min <= max) {if (array[mid] == beSearchedNum) {result = "It is: " + mid;return result;} else if (array[mid] > beSearchedNum) {searchTimes++;max--;} else if (array[mid] < beSearchedNum) {searchTimes++;max++;}mid = (int) ((min + max) / 2);if (searchTimes == searchTimesMax) {result = sorry;break;}}} else {result = sorry;}return result;}}// 如果不使用集合，请仿照下面的写法class ProduceRandom {public static void main(String[] args) {Integer[] intArray = getRandomArray(100, 200, 10);for (Integer i : intArray) {System.out.print(i + " ");}}/** * @param MIN *            :下界 * @param MAX *            ：上界 * @param SUM *            ：总个数 * @return：不同整数的整型数组 */public static Integer[] getRandomArray(final int MIN, final int MAX,final int SUM) {Integer[] intArray = new Integer[SUM];for (int counter = 0; counter < 10; counter++) { // 记录已经产生的随机数个数Integer temp = (int) (Math.random() * (MAX - MIN)) + MIN;// 假设只产生整数，不产生浮点数等其他类型的数int index = temp % SUM;// 因为没有使用集合，为了提高匹配效率，仿真哈希算法，简单的产生下标while (intArray[index] != null) {if (intArray[index] == temp)break;// 值相同时也复制到那个堆内存，相当于什么都没做index = (index + 1) % SUM;}intArray[index] = temp;}return intArray;}}

main方法类：

package chapter5;public class Dichotomy {public static void main(String[] args) {int[] array = Array.generateArray(10);array = Array.setRadomDate(array);Array.sort(array);String result = Array.search(array, 3);System.out.println(result);}}

运行结果：

generate Array... generate Array successful... the Array length is: 10the Array is:2 6 8 1 3 4 4 1 9 5 now we will sort it as 1~9:now the result is: 1 1 2 3 4 4 5 6 8 9 3 wanted be search!now we will search its indexIt is: 3

没查到的运行结果：

package chapter5;public class Dichotomy {public static void main(String[] args) {int[] array = Array.generateArray(10);array = new int[] { 2, 3, 3, 5, 5, 6, 7, 8, 9, 10 };array = Array.setSortDate(array, array);Array.sort(array);String result = Array.search(array, 4);System.out.println(result);}}

generate Array... generate Array successful... the Array length is: 10now we will sort it as 1~9:now the result is: 2 3 3 5 5 6 7 8 9 10 4 wanted be search!now we will search its indexSorry, the system can't find ur Num!