关于数组的操作

操作1,获取数组的最大值和最小值:

获取最大值:

public static int getMax() {int[] arr = { 1, 2, 3, 4, 5, 6, 7 };int max = arr[0];for (int i = 0; i < arr.length; i++) {if (max < arr[i]) {max = arr[i];}}return max;}

获取最小值:

public static int getMin() {int[] arr = { 8, 2, 3, 4, 5, 6, 7 };int min = arr[0];for (int i = 0; i < arr.length; i++) {if (min > arr[i]) {min = arr[i];}}return min;}

操作2:数组排序:

选择排序:

原理示意图:

public static void printArr(int[] arr) {for (int i = 0; i < arr.length; i++) {System.out.print(arr[i] + "\t");}System.out.println();}

int[] arr = { 1, 3, 5, 7, 2, 4, 6 };for (int i = 0; i < arr.length - 1; i++) {// 因为最后一个元素不用在比较了for (int j = i + 1; j < arr.length; j++) {int temp;if (arr[i] > arr[j]) {temp = arr[i];arr[i] = arr[j];arr[j] = temp;}}}

冒泡排序:

原理示意图:

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

操作3:查找是否存在某个元素:

普通查找方式:

public static int search(int[] arr, int target) {if (arr.length > 0) {for (int i = 0; i < arr.length; i++) {if (arr[i] == target) {return i;}}}return -1;}

折半查找法:

原理示意图:

public static int halfSearch(int target) {int[] arr = { 1, 2, 3, 4, 5, 6 };int min, max, mid;min = 0;max = arr.length - 1;mid = (min + max) / 2;while (arr[mid] != target) {if (arr[mid] > target) {max = mid - 1;} else if (arr[mid] < target) {min = mid + 1;}if (min > max) {// 如果数组没有这个元素return -1;}mid = (min + max) / 2;}return mid;}

另一种折半查找方式:

public static int halfSearch2(int target) {int[] arr = { 1, 2, 3, 4, 5, 6, 7 };int min, max, mid;min = 0;max = arr.length - 1;while (min <= max) {mid = (min + max) / 2;if (target > arr[mid]) {min = mid + 1;System.out.println(min);} else if (target < arr[mid]) {max = mid - 1;} else {return mid;}}return -1;}