Java如何实现三个输入整数的最大值与最小值位置互换

实现思路 #

你当前的代码已经正确获取到了三个数的最大值、最小值，但要完成位置互换，首先需要确定最大值、最小值分别存储在first/second/third哪个变量中，仅拿到数值是无法完成位置替换的。

具体实现步骤 #

• 新增两个变量maxIndex、minIndex，用来标记最大值、最小值的位置，用1对应第一个数，2对应第二个数，3对应第三个数
• 比对三个数的取值，给两个标记变量赋值
• 借助临时变量交换对应位置的数值
• 输出交换后的三个数验证结果

修改后的完整代码 #

import java.util.Scanner;
public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("交换三个数中最大值和最小值位置的程序");

        System.out.println("请输入第一个数：");
        int first = scanner.nextInt();

        System.out.println("请输入第二个数：");
        int second = scanner.nextInt();

        System.out.println("请输入第三个数：");
        int third = scanner.nextInt();

        int largest = largest(first, second, third);
        int smallest = smallest(first, second, third);

        System.out.printf("输入的三个数为 %d、%d、%d，最大值是：%d %n", first, second, third, largest);
        System.out.printf("输入的三个数为 %d、%d、%d，最小值是：%d %n", first, second, third, smallest);
        
        // 确定最大最小值的位置
        int maxIndex = 0;
        int minIndex = 0;
        if (first == largest) maxIndex = 1;
        else if (second == largest) maxIndex = 2;
        else maxIndex =3;
        
        if (first == smallest) minIndex = 1;
        else if (second == smallest) minIndex = 2;
        else minIndex =3;
        
        // 交换对应位置的值
        int temp;
        if (maxIndex == 1 && minIndex == 2) {
            temp = first;
            first = second;
            second = temp;
        } else if (maxIndex ==1 && minIndex ==3) {
            temp = first;
            first = third;
            third = temp;
        } else if (maxIndex ==2 && minIndex ==1) {
            temp = second;
            second = first;
            first = temp;
        } else if (maxIndex ==2 && minIndex ==3) {
            temp = second;
            second = third;
            third = temp;
        } else if (maxIndex ==3 && minIndex ==1) {
            temp = third;
            third = first;
            first = temp;
        } else if (maxIndex ==3 && minIndex ==2) {
            temp = third;
            third = second;
            second = temp;
        }
        
        // 输出交换后的结果
        System.out.printf("交换最大最小值位置后的三个数为：%d、%d、%d", first, second, third);
       
        scanner.close();

    }
        public static int largest(int first, int second, int third) {

        int max = first;
        if (second > max) {
            max = second; }

        if (third > max) {
            max = third; }

        return max; }

        public static int smallest(int first, int second, int third) {

        int min = first;
        if (second < min) {
            min = second; }

        if (third < min) {
            min = third; }

        return min; }
}

优化方案 #

如果不想写多分支判断，可以把三个数放到数组中处理，逻辑更简洁：

// 把三个数存入数组
int[] nums = {first, second, third};
int maxIdx = 0, minIdx = 0;
for (int i = 1; i < nums.length; i++) {
    if (nums[i] > nums[maxIdx]) maxIdx = i;
    if (nums[i] < nums[minIdx]) minIdx = i;
}
// 交换数组对应位置的值
int temp = nums[maxIdx];
nums[maxIdx] = nums[minIdx];
nums[minIdx] = temp;
// 把数组值写回原变量
first = nums[0];
second = nums[1];
third = nums[2];

内容的提问来源于stack exchange，提问作者D. Georgieva