package com.dataStructure.arrayList;
import java.util.Arrays;
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 static int[] reverseArray(int[] origin) {
for (int i = 0, j = origin.length - 1; i < origin.length / 2; i++, j--) {
int temp = origin[i];
origin[i] = origin[j];
origin[j] = temp;
}
return origin;
}
/**
* 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 static int[] removeZero(int[] oldArray) {
int count = 0;
int[] newArray = new int[oldArray.length];
for (int i = 0, j = 0; i < oldArray.length; i++) {
if (oldArray[i] == 0) {
count++;
continue;
} else
newArray[j++] = oldArray[i];
}
int[] temp = new int[newArray.length-count];
System.arraycopy(newArray, 0, temp, 0, temp.length);
newArray = temp;
return 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
*/
// bug
public static int[] merge(int[] array1, int[] array2) {
int len1 = array1.length;
int len2 = array2.length;
int[] array3 = new int[len1 + len2];
int len3 = len1 + len2;
int a1 = 0;
int a2 = 0;
int a3 = 0;
while (len3 > 0) {
if (a1 == len1 || a2 == len2) {
break;
}
if (array1[a1] < array2[a2]) {
array3[a3] = array1[a1];
a1++;
a3++;
} else {
if (array1[a1] > array2[a2]) {
array3[a3] = array2[a2];
a2++;
a3++;
} else {
array3[a3] = array1[a1];
a1++;
a2++;
a3++;
}
}
len3--;
}
if (a1 == len1 && a2 == len2) {
return array3;
}
if (a1 == len1) {
for (int i = a2; i < len2; i++) {
array3[a3] = array2[a2];
a3++;
}
} else {
for (int i = a1; i < len1; i++) {
array3[a3] = array1[a1];
a3++;
}
}
int[] temp = new int[a3];
System.arraycopy(array3, 0, temp, 0, temp.length);
array3 = temp;
return array3;
}
/**
* 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 static int[] grow(int[] oldArray, int size) {
int[] newArray = new int[oldArray.length + size];
for (int i = 0; i < oldArray.length; i++) {
newArray[i] = oldArray[i];
}
return 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 static int[] fibonacci(int max) {
if (max == 1)
return new int[0];
else {
int[] arr = new int[max];
arr[0] = 1;
arr[1] = 1;
int val = 0;
int f1 = 1;
int f2 = 1;
int index = 2;
while (val < max) {
val = f1 + f2;
if(val>max){
break;
}
f1 = f2;
f2 = val;
arr[index++] = val;
}
int[] temp = new int[index];
System.arraycopy(arr, 0, temp, 0, temp.length);
arr = temp;
return arr;
}
}
/**
* 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 static int[] getPrimes(int max) {
int val = 2; // 数值增加
int index = 0; // 数组索引
int[] primes = new int[max]; // 存放素数数组
boolean flag = true;
while (val < max) {
for (int i = 2; i <val; i++) { // 判定素数
if (val % i == 0) {
flag = false;
break;
}
}
if (flag) {
primes[index++] = val;
}
val++;
flag = true;
}
int[] temp = new int[index];
System.arraycopy(primes, 0, temp, 0, temp.length);
primes = temp;
return primes;
}
private static void rangeCheck(int max) {
if (max <= 0)
throw new IndexOutOfBoundsException(" max ");
}
/**
* 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 static int[] getPerfectNumbers(int max) {
rangeCheck(max);
int[] newArray = new int[max];
int count = 0;
for (int i = 1; i < max; i++) {
if (max % i == 0) {
newArray[count] = i;
count++;
}
}
int sum = 0;
for (int i = 0; i < max; i++) {
sum = sum + newArray[i];
}
if (sum == max) {
int [] temp = new int[count];
System.arraycopy(newArray, 0, temp, 0, temp.length);
newArray = temp;
System.out.println(sum);
return newArray;
} else {
System.out.println("max is not perfectNumber");
return null;
}
}
/**
* 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 static String join(int[] array, String seperator) {
StringBuilder str = new StringBuilder();
for (int i = 0; i < array.length; i++) {
str.append(array[i]);
if (i < array.length - 1)
str.append(seperator);
}
return str.toString();
}
public static void main(String[] args) {
int i = 1;
while(true){
int[] temp = getPerfectNumbers(i++);
if(temp!=null){
System.out.println(Arrays.toString(temp));
}
}
}
}