2017.11.29_实验6数组
1.编写程序，用一维数组保存20个学生的某门课程的成绩，计算平均成绩，并输出。
package ex05;
public class AverageGrade {
public static void main(String[] args) {
// TODO Auto-generated method stub
double []a = { 100, 100, 100, 100, 100, 50, 50, 50, 50, 50, 100, 100,
100, 100, 100, 50, 50, 50, 50, 50 };
double sum = 0;
for (int i = 0; i < a.length; i++) {
sum += a[i];
}
System.out.println("20个学生的平均成绩为：" + sum / 20);
}
}
/*20个学生的平均成绩为：75.0*/2.对上题中数组中的数据进行从小到大排序（使用冒泡法和选择法）。
package ex05;
public class Sort {
public static void main(String[] args) {
// TODO Auto-generated method stub
double a[] = { 1, 3, 4, 5, 2 };
for (int i = 0; i < a.length; i++) {
System.out.print(a[i] + " ");
}
System.out.println();
for (int i = 0; i < a.length - 1; i++) {
for (int j = 0; j < a.length - 1; j++) {
if (a[j] > a[j + 1]) {
double temp = a[j];
a[j] = a[j + 1];
a[j + 1] = temp;
}
}
}
System.out.println("对a[]从小到大冒泡：");
for (int i = 0; i < a.length; i++) {
System.out.print(a[i] + " ");
}
System.out.println();
double b[] = { 3, 6, 9, 1, 0 };
for (int i = 0; i < b.length; i++) {
for (int j = i + 1; j < b.length; j++) {
if (b[j] < b[i]) {
double temp = b[i];
b[i] = b[j];
b[j] = temp;
}
}
}
System.out.println("对b[]从小到大选择排序：");
for (int i = 0; i < b.length; i++) {
System.out.print(b[i] + " ");
}
}
}
/*
1.0 3.0 4.0 5.0 2.0
对a[]从小到大冒泡：
1.0 2.0 3.0 4.0 5.0
对b[]从小到大选择排序：
0.0 1.0 3.0 6.0 9.0
*/3.
定义一个Student类，包括姓名、学号、成绩三个成员变量以及getName()、getNo()、getScore()三个方法。在构造函数中初始化姓名、学号、成绩三个成员变量。定义一个大小为20的类型为Student的数组，按学生成绩的高低，依次输出姓名和成绩。
package work03;
public class Student {
private String name, no;
private double score;
public Student(String name, String no, double score) {
super();
this.name = name;
this.no = no;
this.score = score;
}
public String getName() {
return name;
}
public String getNo() {
return no;
}
public double getScore() {
return score;
}
public void display() {
System.out.println(name + " " + no + " " + score + " ");
}
}
package work03;
import java.util.Scanner;
public class TestStudent {
public static void main(String[] args) {
// TODO Auto-generated method stub
Student[] a = new Student[5];
String name, no;
double score;
Scanner sc = new Scanner(System.in);
System.out.println("请输入：");
for (int i = 0; i < 5; i++) {
name = sc.next();
no = sc.next();
score = sc.nextDouble();
a[i] = new Student(name, no, score);
}
for (int i = 0; i < 5; i++) {
a[i].display();
}
Sortt.sort(a);
System.out.println("按成绩降序排序：");
for (int i = 0; i < 5; i++) {
a[i].display();
}
}
}
/*
请输入：
小明 2017001 89
小李 2017002 60
小辉 2017003 78
小红 2017004 100
小华 2017005 92
小明 2017001 89.0
小李 2017002 60.0
小辉 2017003 78.0
小红 2017004 100.0
小华 2017005 92.0
按成绩降序排序：
小红 2017004 100.0
小华 2017005 92.0
小明 2017001 89.0
小辉 2017003 78.0
小李 2017002 60.0
*/package work03;
public class Sortt {
public static void sort(Student[] a) {
Student temp;
for (int i = 0; i < 5; i++) {
for (int j = i + 1; j < 5; j++) {
if (a[i].getScore() < a[j].getScore()) {
temp = a[i];
a[i] = a[j];
a[j] = temp;
}
}
}
}
}
4.编程求一个3×3矩阵的主对角线元素之和及次对角元素之和。
package work03;
public class Sum {
public static void main(String[] args) {
// TODO Auto-generated method stub
int[][] a = new int[][] { { 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 } };
getSum(a);
}
private static void getSum(int[][] a) {
// TODO Auto-generated method stub
double sum1 = 0;
double sum2 = 0;
for (int i = 0; i < a.length; i++) {
for (int j = 0; j < a[i].length; j++) {
if (i == j) {
sum1 += a[i][j];
}
if (j == a.length - 1 - i) {
sum2 += a[i][j];
}
}
}
System.out.println("主对角线之和为：" + sum1 + " 副对角线之和为：" + sum2);
}
}
/*主对角线之和为：15.0 副对角线之和为：15.0
*/
5.将一个5×5的二维数组转置到另一个5×5的二维数组（即沿主对角线翻转）。
package work03;
public class Sum {
public static void main(String[] args) {
// TODO Auto-generated method stub
int[][] a = { { 1, 1, 1, 1, 1 }, { 2, 2, 2, 2, 2 }, { 3, 3, 3, 3, 3 },
{ 4, 4, 4, 4, 4 }, { 5, 5, 5, 5, 5 } };
for (int i = 0; i < a.length; i++) {
for (int j = 0; j < a[i].length; j++) {
System.out.print(a[i][j] + " ");
}
System.out.println();
}
System.out.println("转置后的矩阵：");
zhuanzhi(a);
}
private static void zhuanzhi(int[][] a) {
// TODO Auto-generated method stub
/*
* int[][] b=new int[5][5];
* for(int i=0;i6.编程找一个二维数组的鞍点，即该位置上的元素在该行上最大、在列上最小。
package work03;
import java.util.Scanner;
public class Andian {
public static void main(String[] args) {
int a[][] = new int[111][111];
Scanner sc = new Scanner(System.in);
System.out.println("请输入行和列");
int n = sc.nextInt();
int m = sc.nextInt();
int i, j;
for (i = 0; i < n; i++) {
for (j = 0; j < m; j++) {
a[i][j] = sc.nextInt();
}
}
int max, maxj;
boolean flag = true;
for (i = 0; i < n; i++) {
max = a[i][0];
maxj = 0;
for (j = 0; j < m; j++) {
if (max < a[i][j]) {
max = a[i][j];
maxj = j;
}
}
flag = true;
for (int k = 0; k < n; k++) {
if (max > a[k][maxj]) {
flag = false;
continue;
}
}
if (flag) {
System.out.println("行号: " + i + " 列号: " + j + " 鞍点:" + max);
break;
}
}
if (flag == false) {
System.out.println("不存在鞍点");
}
}
}
/*
请输入行和列
2 3
1 2 3
4 5 6
行号: 0 列号: 3 鞍点:3
*/