package com.coderising.array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
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
* 11 01 11|
*/
public void reverseArray(int[] origin){
int len = origin.length-1;
for (int i = 0; i <((0 == len%2) ? len/2 :(len+1)/2) ; i++) {
origin[i] = origin[i]^origin[len-i];
origin[len-i] = origin[len-i]^origin[i];
origin[i] = origin[i]^origin[len-i];
}
}
/**
* 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){
//get count
int count = 0;
for (int i : oldArray) {
if(0 != i) {
count++;
}
}
//remove zero
int newArray[] = new int[count];
int j=0;
for (int i : oldArray) {
if(0 != i) {
newArray[j++] = i;
}
}
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
*/
public Integer[] merge(int[] array1, int[] array2){
if (null==array1 || null == array2 || 0 == array1.length || 0 == array2.length) {
new IllegalArgumentException("参数不允许为空数组!");
}
int i=0,j=0;
ArrayList<Integer> mergedList = new ArrayList<Integer>();
while (true) {
if (j == array2.length-1 || i == array1.length-1) {
break;
}
if (array1[i] < array2[j]) {
mergedList.add(array1[i]);
i++;
}else if (array1[i] > array2[j]) {
mergedList.add(array2[j]);
j++;
}else {
mergedList.add(array2[j]);
i++;
j++;
}
}
//put the least part of one array into list
if (i == array1.length) {
for (int k = j; k < array2.length; k++) {
mergedList.add(array2[k]);
}
}else {
for (int k = i; k < array1.length; k++) {
mergedList.add(array1[k]);
}
}
return arrayListToInteger(mergedList);
}
private Integer[] arrayListToInteger(ArrayList<Integer> arrayList) {
Integer tempArray[] = new Integer[arrayList.size()];
int i=0;
for (Integer integer : arrayList) {
tempArray[i++] = integer;
}
return tempArray;
}
/**
* 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){
if (null == oldArray || size<= 0) {
new IllegalArgumentException("数组为空或者长度非法!!");
}
int newArray[] = new int[oldArray.length + size];
System.arraycopy(oldArray, 0, newArray, 0, oldArray.length);
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 Integer[] fibonacci(int max){
if ( 1 == max ) {
return new Integer[0];
}
ArrayList<Integer> arrayList = new ArrayList<Integer>();
arrayList.add(1);
arrayList.add(1);
int i=0,j=1;
while (arrayList.get(i)+arrayList.get(j) < max) {
arrayList.add(arrayList.get(i)+arrayList.get(j));
i++;
j++;
}
return arrayListToInteger(arrayList);
}
/**
* 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 Integer[] getPrimes(int max){
ArrayList<Integer> arrayList = new ArrayList<Integer>();
boolean isPrimes = true;
for (int i = 2; i < max; i++) {
isPrimes = true;
for (int j = 2; j <= Math.sqrt(i) ; j++) {
if (0 == i % j) {
isPrimes = false;
break;
}
}
if (isPrimes) {
arrayList.add(i);
}
}
return arrayListToInteger(arrayList);
}
/**
* 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 Integer[] getPerfectNumbers(int max){
ArrayList<Integer> arrayList = new ArrayList<Integer>();
int sum = 0;
for (int i = 2; i < max; i++) {
sum = 0;
//the factor is less than half of a number
for (int j = 1; j <= (i+1)/2; j++) {
if (0 == i%j) {
sum += j;
}
}
if (sum == i) {
arrayList.add(i);
}
}
return arrayListToInteger(arrayList);
}
/**
* 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 i : array) {
sb.append(i).append(seperator);
}
sb.deleteCharAt(sb.length()-1);
return sb.toString();
}
}