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1、功能：随机生成n个数并求和
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2、以下是代码（代码里取n=10）：
public class Sum {
public static void main(String[] args) {
double i;//随机生成的数字
double sum=0;
for(int j=0;j10;j++)
{
i=(double) Math.random();
System.out.println("第"+(j+1)+"次生成的数字是"+i);
sum+=i;
}
System.out.println("它们的和是:"+sum);
}
}
下面是我自己定的一个int数组排序的工具，希望对你有帮助。
package net.ftng.util.Order;
public class IntArrayOrder {
/**
* @param args
*/
public static void main(String[] args) {
int[] a = { 12, 6, 14, 7, 18, 9 };
System.out.print("noOrderByAnything====:");
for (int t : a) {
System.out.print(t + " ");
}
System.out.println();
System.out.print("orderByAscend====:");
int[] temp = lightOrderByAscend(a);
for (int t : temp) {
System.out.print(t + " ");
}
System.out.println();
System.out.print("orderByDescend====:");
temp = lightOrderByDescend(a);
for (int t : temp) {
System.out.print(t + " ");
}
}
static public int[] lightOrderByAscend(int[] args) {
try {
int temp;
int[] tempargs = args.clone();
int argsLength = tempargs.length;
for (int i = 0; i argsLength; i++) {
for (int j = i + 1; j argsLength; j++) {
if (tempargs[i] tempargs[j]) {
temp = tempargs[i];
tempargs[i] = tempargs[j];
tempargs[j] = temp;
}
}
}
return tempargs;
} catch (Exception e) {
return null;
}
}
static public int[] deepOrderByAscend(int[] args) {
try {
int temp;
int argsLength = args.length;
for (int i = 0; i argsLength; i++) {
for (int j = i + 1; j argsLength; j++) {
if (args[i] args[j]) {
temp = args[i];
args[i] = args[j];
args[j] = temp;
}
}
}
return args;
} catch (Exception e) {
return null;
}
}
static public int[] lightOrderByDescend(int[] args) {
try {
int temp;
int[] tempargs = args.clone();
int argsLength = tempargs.length;
for (int i = 0; i argsLength; i++) {
for (int j = i + 1; j argsLength; j++) {
if (tempargs[i] tempargs[j]) {
temp = tempargs[i];
tempargs[i] = tempargs[j];
tempargs[j] = temp;
}
}
}
return tempargs;
} catch (Exception e) {
return null;
}
}
static public int[] deepOrderByDescend(int[] args) {
try {
int temp;
int argsLength = args.length;
for (int i = 0; i argsLength; i++) {
for (int j = i + 1; j argsLength; j++) {
if (args[i] args[j]) {
temp = args[i];
args[i] = args[j];
args[j] = temp;
}
}
}
return args;
} catch (Exception e) {
return null;
}
}
}
选择排序法：
public class TSort{
public static void main(String args[]){
int a[]={12,45,2,5,26,56};
for(int i=0;ia.length-1;i++){
int t;
for(int j=i+1;ja.length;j++){
if(a[i]a[j]){
t=a[i];a[i]=a[j];a[j]=t;
}
}
}
for(int i=0;ia.length;i++){
System.out.print(a[i]+" ");
}
}
}
package huda.laogao.ON_20121216;
import java.util.*;
public class GetEquation {
ArrayListInteger params = null;// 进行加减的数，长度设为n
int result = 0;// 结果
public GetEquation(ArrayListInteger params, int result) {
this.params = params;
this.result = result;
}
public void run() {
int size = params.size();
if (size == 1) {
if (params.get(0) == result)
System.out.println(result + "=" + result);
else
System.out.println("Invalid");
return;
}
int[][] matrix = getMatrix(size - 1);
int m = matrix.length;// 行数
int count = 0;// 记录符合结果的组合数
for (int i = 0; i m; i++) {
int now = params.get(0);// 进行加减的结果，初始为第一个值
// 从第二个数开始进行加或减，加的话就相当于该数乘上1，然后加到结果上，
// 减的就相当于该数乘上-1，然后加到结果上
for (int j = 1; j size; j++) {
now += matrix[i][j - 1] * params.get(j);
}
// System.out.println(now);
// 判断结果
if (now == result) {
count++;// 组合数加1
System.out.print(params.get(0));
for (int j = 1; j size; j++) {
if (matrix[i][j - 1] == 1)
System.out.print("+" + params.get(j));
else
System.out.print("-" + params.get(j));
}// for j
System.out.println("=" + result);
}// if
}// for i
if (count == 0)
System.out.println("Invalid");
}
public int[][] getMatrix(int n) {
int m = (int) Math.pow(2, n);
int matrix[][] = new int[m][n];
for (int i = 0; i n; i++) {
int num = (int) Math.pow(2, i + 1);
// 总共分 2^(i+1)块，如i=0，即该矩阵的第一列，可分为2块，上一块取1，下一块取-1
int size = (int) Math.pow(2, n - i - 1);
// 每块的大小为2^(n-i-1)，如n=3，i=0，每块的大小为4，即前4个为1，后4个为-1
int flag = 1;// 先为+
for (int j = 0; j num; j++) {
for (int k = 0; k size; k++) {
matrix[k + j * size][i] = flag;
}
flag *= -1;
}
}
return matrix;
}
public void print(int[][] matrix) {
for (int i = 0; i matrix.length; i++) {
for (int j = 0; j matrix[i].length; j++) {
System.out.print(matrix[i][j] + "\t");
}
System.out.println();
}
}
public static void main(String args[]) {
ArrayListInteger params = new ArrayListInteger();
params.add(1);
params.add(2);
params.add(3);
params.add(4);
int result = 10;
GetEquation ge = new GetEquation(params, result);
ge.run();
}
}
运行结果为：1+2+3+4=10
注：难点为获取加减矩阵，可辅助print()函数帮助理解
望采纳
public class mainClass {
public mainClass() {
}
public static void main(String []args){
int [] num = new int[35];
boolean [] flag = new boolean[35];
int count = 0;
for(int i=0;i35;i++)
{
num[i] = i + 1;
flag[i] = true;
}
while(count!=7){
int k=(int)(Math.random()*35);
if(flag[k]){
System.out.println(num[k]);
flag[k]=false;
count++;
}
}
}
}
Java 算法:
public class Sort {
public void swap(int a[], int i, int j) {
int tmp = a[i];
a[i] = a[j];
a[j] = tmp;
}
public int partition(int a[], int low, int high) {
int pivot, p_pos, i;
p_pos = low;
pivot = a[p_pos];
for (i = low + 1; i = high; i++) {
if (a[i] pivot) {
p_pos++;
swap(a, p_pos, i);
}
}
swap(a, low, p_pos);
return p_pos;
}
public void quicksort(int a[], int low, int high) {
int pivot;
if (low high) {
pivot = partition(a, low, high);
quicksort(a, low, pivot - 1);
quicksort(a, pivot + 1, high);
}
}
public static void main(String args[]) {
int vec[] = new int[] { 37, 47, 23, -5, 19, 56 };
int temp;
//选择排序法(Selection Sort)
long begin = System.currentTimeMillis();
for (int k = 0; k 1000000; k++) {
for (int i = 0; i vec.length; i++) {
for (int j = i; j vec.length; j++) {
if (vec[j] vec[i]) {
temp = vec[i];
vec[i] = vec[j];
vec[j] = temp;
}
}
}
}
long end = System.currentTimeMillis();
System.out.println("选择法用时为：" + (end - begin));
//打印排序好的结果
for (int i = 0; i vec.length; i++) {
System.out.println(vec[i]);
}
// 冒泡排序法(Bubble Sort)
begin = System.currentTimeMillis();
for (int k = 0; k 1000000; k++) {
for (int i = 0; i vec.length; i++) {
for (int j = i; j vec.length - 1; j++) {
if (vec[j + 1] vec[j]) {
temp = vec[j + 1];
vec[j + 1] = vec[j];
vec[j] = temp;
}
}
}
}
end = System.currentTimeMillis();
System.out.println("冒泡法用时为：" + (end - begin));
//打印排序好的结果
for (int i = 0; i vec.length; i++) {
System.out.println(vec[i]);
}
//插入排序法(Insertion Sort)
begin = System.currentTimeMillis();
for (int k = 0; k 1000000; k++) {
for (int i = 1; i vec.length; i++) {
int j = i;
while (vec[j - 1] vec[i]) {
vec[j] = vec[j - 1];
j--;
if (j = 0) {
break;
}
}
vec[j] = vec[i];
}
}
end = System.currentTimeMillis();
System.out.println("插入法用时为：" + (end - begin));
//打印排序好的结果
for (int i = 0; i vec.length; i++) {
System.out.println(vec[i]);
}
//快速排序法(Quick Sort)
Sort s = new Sort();
begin = System.currentTimeMillis();
for (int k = 0; k 1000000; k++) {
s.quicksort(vec, 0, 5);
}
end = System.currentTimeMillis();
System.out.println("快速法用时为：" + (end - begin));
//打印排序好的结果
for (int i = 0; i vec.length; i++) {
System.out.println(vec[i]);
}
}
}
以下是运行结果：
选择法用时为：234
56
47
37
23
19
-5
冒泡法用时为：172
56
47
37
23
19
-5
插入法用时为：78
56
47
37
23
19
-5
快速法用时为：297
56
47
37
23
19
-5