package com.sl.test20170304.arrayutil;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.junit.Test;
public class ArrayUtil {
/**
* 给定一个整形数组a , 对该数组的值进行置换
例如： a = [7, 9 , 30, 3] , 置换后为 [3, 30, 9,7]
如果 a = [7, 9, 30, 3, 4] , 置换后为 [4,3, 30 , 9,7]
* @param origin
* @return
*/
public void reverseArray(int[] origin){
int low = 0;
int high = origin.length - 1;
while(low < high){
int temp = 0;
temp = origin[low];
origin[low] = origin[high];
origin[high] = temp;
low++;
high--;
}
}
@Test
public void test1(){
int[] arr = {7, 9 , 30, 3};
reverseArray(arr);
System.out.println(Arrays.toString(arr));
}
/**
* 现在有如下的一个数组： int oldArr[]={1,3,4,5,0,0,6,6,0,5,4,7,6,7,0,5}
* 要求将以上数组中值为0的项去掉，将不为0的值存入一个新的数组，生成的新数组为：
* {1,3,4,5,6,6,5,4,7,6,7,5}
* @param oldArray
* @return
*/
public int[] removeZero(int[] oldArray){
int[] arr = new int[oldArray.length];
int num = 0;
for(int i = 0;i < oldArray.length;i++){
if(oldArray[i] != 0){
arr[num] = oldArray[i];
num++;
}
}
int[] newArray = Arrays.copyOf(arr, num);
return newArray;
}
@Test
public void test2(){
int oldArr[] = {1,3,4,5,0,0,6,6,0,5,4,7,6,7,0,5};
int[] newArray = removeZero(oldArr);
System.out.println(Arrays.toString(newArray));
}
/**
* 给定两个已经排序好的整形数组， a1和a2 , 创建一个新的数组a3, 使得a3 包含a1和a2 的所有元素， 并且仍然是有序的
* 例如 a1 = [3, 5, 7,8] a2 = [4, 5, 6,7] 则 a3 为[3,4,5,6,7,8] , 注意： 已经消除了重复
* @param array1
* @param array2
* @return
*/
public int[] merge(int[] array1, int[] array2){
int len1 = array1.length;
int len2 = array2.length;
int[] arr = new int[len1 + len2];
int len = 0;
int i = 0;
int j = 0;
int min = 0;
while(i < len1 && j< len2){
if(array1[i] == array2[j]){
min = array1[i];
arr[len] = min;
i++;
j++;
len++;
continue;
}
if(array1[i] > array2[j]){
min = array2[j];
arr[len] = min;
j++;
len++;
continue;
}
if(array1[i] < array2[j]){
min = array1[i];
arr[len] = min;
i++;
len++;
continue;
}
}
if(i > j){
for(int k = j;k < len2;k++){
arr[len] = array2[k];
len++;
}
}
if(i < j){
for(int k = i;k < len1;k++){
arr[len] = array1[k];
len++;
}
}
int[] newArray = Arrays.copyOf(arr, len);
return newArray;
}
@Test
public void test3(){
int[] a1 = {3, 7, 9,10,34,78,123};
int[] a2 = {4, 5, 6,7,56,34,345,2432,545345345};
int[] newArray = merge(a1, a2);
System.out.println(Arrays.toString(newArray));
}
/**
* 把一个已经存满数据的数组 oldArray的容量进行扩展， 扩展后的新数据大小为oldArray.length + size
* 注意，老数组的元素在新数组中需要保持
* 例如 oldArray = [2,3,6] , size = 3,则返回的新数组为
* [2,3,6,0,0,0]
* @param oldArray
* @param size
* @return
*/
public int[] grow(int [] oldArray, int size){
int[] newArray = Arrays.copyOf(oldArray, oldArray.length + size);
return newArray;
}
@Test
public void test4(){
int[] oldArray = {2,3,6};
int[] newArray = grow(oldArray,3);
System.out.println(Arrays.toString(newArray));
}
/**
* 斐波那契数列为：1，1，2，3，5，8，13，21...... ，给定一个最大值， 返回小于该值的数列
* 例如， max = 15 , 则返回的数组应该为 [1，1，2，3，5，8，13]
* max = 1, 则返回空数组 []
* @param max
* @return
*/
public int[] fibonacci(int max){
int[] arr = new int[100];
int len = 2;
int f1 = 1;
int f2 = 1;
int f3 = f1 + f2;
if(max == 1){
return new int[0];
}
arr[0] = f1;
arr[1] = f2;
while(f3 <= max){
arr[len] = f3;
len++;
f1 = f2;
f2 = f3;
f3 = f1 + f2;
}
int[] newArray = Arrays.copyOf(arr, len);
return newArray;
}
@Test
public void test5(){
int[] newArray = fibonacci(100);
System.out.println(Arrays.toString(newArray));
}
/**
* 返回小于给定最大值max的所有素数数组
* 例如max = 23, 返回的数组为[2,3,5,7,11,13,17,19]
* @param max
* @return
*/
public int[] getPrimes(int max){
int[] arr = new int[max];
int len = 0;
for(int i = 0;i <= max;i++){
if(i == 0 || i == 1){
continue;
}
if(isPrime(i)){
arr[len] = i;
len++;
}
}
int[] newArray = Arrays.copyOf(arr, len);
return newArray;
}
private boolean isPrime(int n){
for(int i=2;i<=n/2;i++){
if(n%i == 0)
return false;
}
return true;
}
@Test
public void test6(){
int max = 100;
int[] newArray = getPrimes(max);
System.out.println(Arrays.toString(newArray));
}
/**
* 所谓“完数”， 是指这个数恰好等于它的因子之和，例如6=1+2+3
* 给定一个最大值max， 返回一个数组， 数组中是小于max 的所有完数
* @param max
* @return
*/
public int[] getPerfectNumbers(int max){
int[] arr = new int[max];
int len = 0;
for(int i = 0;i <= max;i++){
if(i == 0 || i == 1){
continue;
}
if(isPerfectNumber(i)){
arr[len] = i;
len++;
}
}
int[] newArray = Arrays.copyOf(arr, len);
return newArray;
}
private boolean isPerfectNumber(int num){
List<Integer> list = new ArrayList<Integer>();
int sum = 0;
for(int i = 1;i < num;i++){
if(num % i == 0){
list.add(i);
}
}
for(int j : list){
sum += j;
}
return sum == num ? true : false;
}
@Test
public void test7(){
int max = 100000;
int[] newArray = getPerfectNumbers(max);
System.out.println(Arrays.toString(newArray));
}
/**
* 用seperator 把数组 array给连接起来
* 例如array= [3,8,9], seperator = "-"
* 则返回值为"3-8-9"
* @param array
* @param s
* @return
*/
public String join(int[] array, String seperator){
StringBuilder sb = new StringBuilder();
for(int num : array){
sb.append(num).append(seperator);
}
String str = sb.toString();
str = str.substring(0, str.lastIndexOf(seperator));
return str;
}
@Test
public void test8(){
int[] arr = {1,2,5,6,78,34,332,4452,4342,3,435,233};
System.out.println(join(arr,"-"));
}
}