package com.coderising.array;
import java.lang.reflect.Array;
import java.util.*;
import com.coding.basic.ArrayList;
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 int[] reverseArray(int[] origin) {
if (origin != null && origin.length > 0) {
int size = origin.length;
int[] intarray = new int[size];
for (int i = 0; i < size; i++) {
intarray[i] = origin[size - 1 - i];
}
origin = intarray;
} else if (origin != null && origin.length == 0) {
} else {
throw new NullPointerException();
}
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 int[] removeZero(int[] oldArray) {
if (oldArray != null) {
int[] intarry = new int[oldArray.length];
int x = 0;
int y = 0;
for (int i = 0; i < oldArray.length; i++) {
if (oldArray[i] != 0) {
intarry[y] = oldArray[i];
y++;
} else {
x++;
}
}
int[] newarray = new int[y];
System.arraycopy(intarry, 0, newarray, 0, y);
return newarray;
} else {
throw new NullPointerException();
}
}
/**
* 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 count = array2.length;
array2 = grow(array2, array1.length);
System.arraycopy(array1, 0, array2, count, array1.length);
Arrays.sort(array2);
int[] array3 = new int[array2.length];
array3[0] = array2[0];
int x = 0;
for (int i = 1; i < array2.length; i++) {
if (array2[i] != array3[x]) {
array3[x + 1] = array2[i];
x++;
}
}
int[] array4 = new int[x + 1];
System.arraycopy(array3, 0, array4, 0, x + 1);
return array4;
}
/**
* 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 = 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 int[] fibonacci(int[] array, int max) {
int[] array0 = new int[array.length];
int x = 0;
int y = 0;
for (int i = 0; i < array.length; i++) {
if (array[i] < max) {
array0[y] = array[i];
y++;
} else {
x++;
}
}
int[] array1 = new int[y];
return Arrays.copyOf(array0, y);
}
/**
* 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) {
if(max<=2)
{return new int[]{};
}
int[] temp = new int[max];
int index = 0;
for (int i = 2; i < max; i++) {
boolean flag = true;
for (int j = 2; j <= Math.sqrt(i); j++) {
if(i % j == 0){
flag = false;
}
}
if(flag){temp[index++] = i;}
}
return Arrays.copyOf(temp, index);
}
/**
* 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) {
if(max <= 2) return new int[]{};
int[] array = new int[max];
int index = 0;
for (int i = 2; i < max; i++) {
int x = 0;
for (int j = 1; j <= Math.sqrt(i); j++) {
if(j == 1) {
x += 1;
}else{
if(i % j == 0){
x += j + i/j;
}
}
}
if(x == i) array[index++] = i;
}
return Arrays.copyOf(array, index);
}
/**
* 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) {
if(array.length == 0){
return "";
}
StringBuilder sb = new StringBuilder();
for (int i : array) {
sb.append(i).append(seperator);
}
String temp = sb.toString();
return temp.substring(0,temp.length()-1);
}
}