【Java基础】选择排序、冒泡法排序、二分法查找

[title2]1.选择排序：[/title2]

//改进后的选择排序，减少交换的次数public static void sortSelect(int arr[]) {//用于存放最小数的下标int s;for (int i = 0; i < arr.length; i++) {s = i;for (int j = i + 1; j < arr.length; j++) {if (arr[s] > arr[j]) {//记录最小值的下标值s = j;}}//如果最小数的下标值改变，则交换if (s != i) {int temp = arr[i];arr[i] = arr[s];arr[s] = temp;}}}[title2]2.冒泡法排序[/title2]

public static void BubbleSort(int[] arr) {for (int i = 0; i < arr.length - 1; i++) {for (int j = 0; j < arr.length - i - 1; j++) {if (arr[j] < arr[j + 1]) {int temp = arr[j];arr[j] = arr[j + 1];arr[j + 1] = temp;}}}}

3.二分法搜索

/*** @param a	需要搜索的数组* @param num	需要搜索的数字* @return		搜索到的数字的下标，没有找到则返回-1*/public static int searchByBinary(int[] a, int num) {if (a.length == 0) {return -1;}int start = 0;int end = a.length;int m = (start + end) / 2;while (start <= end) {if (a[m] == num) {return m;}if (a[m] > num) {end = m - 1;}if (a[m] < num) {start = m + 1;}m = (start + end) / 2;}return -1;}