package com.coderising.array;
import java.awt.Dialog.ModalExclusionType;
import java.awt.Dimension;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Dictionary;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.StringJoiner;
import java.util.TreeSet;
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) {
int length = origin.length;
int[] nArr = new int[length];
for (int i = 0; i < length; i++) {
nArr[i] = origin[length - i - 1];
}
return nArr;
}
/**
* 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[] newArray = new int[oldArray.length];
int size = 0;
for (int i : oldArray) {
if (i != 0) {
newArray[size] = i;
size++;
}
}
return Arrays.copyOf(newArray, size);
}
/**
* 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 static int[] merge(int[] array1, int[] array2) {
Set<Integer> set = new TreeSet<Integer>();
for (int i = 0; i < array1.length; i++) {
set.add(array1[i]);
}
for (int i = 0; i < array2.length; i++) {
set.add(array2[i]);
}
int[] newArray = new int[set.size()];
int j = 0;
for (Integer i : set) {
newArray[j++] = i;
}
return 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 static 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 static int[] fibonacci(int max) {
if (max <= 1) {
return null;
}
int[] arrFib = new int[max / 2 + 2];
int current = 0;
int temp = 1;
int pre = 1;
int next = 2;
arrFib[current++] = 1;
arrFib[current++] = 1;
do {
arrFib[current++] = next;
temp = pre;
pre = next;
next = next + temp;
} while (next <= max);
return Arrays.copyOf(arrFib, current);
}
/**
* 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) {
if (max < 2) {
return null;
}
int[] arrPrimes = new int[max];
int current = 0;
arrPrimes[current++] = 2;
Boolean isPrime = true;
for (int i = 3; i < max; i++) {
isPrime = true;
for (Integer j : arrPrimes) {
if (j == 0) {
break;
}
if (i % j == 0) {
isPrime = false;
break;
}
}
if (isPrime == true) {
arrPrimes[current++] = i;
}
}
System.out.println(current);
return Arrays.copyOf(arrPrimes, current);
}
/**
* 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) {
if (max < 6) {
return null;
}
int[] arrPerNums = new int[max / 6 + 1];
int current = 0;
arrPerNums[current++] = 6;
for (int i = 7; i < max; i++) {
int sum = 1;
for (int j = 2; j < i / 2+1; j++) {
if (i % j == 0) {
sum += j;
}
}
if (sum == i) {
arrPerNums[current++] = i;
}
}
return Arrays.copyOf(arrPerNums, current);
}
/**
* 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 sb = new StringBuilder();
for (int i = 0; i < array.length; i++) {
sb.append("-");
sb.append(array[i]);
}
return sb.toString().substring(1);
}
}