/**
*
*/
package com.coderising.array;
/**
* @author patchouli
*
*/
public class ArrayUntil {
/**
* 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 size = origin.length;
if (size == 0 || size == 1) {
return;
}
int temp = 0;
for (int i = 0; i < size / 2; i++) {
temp = origin[i];
origin[i] = origin[size - 1 - i];
origin[size - 1 - i] = temp;
}
}
/**
* 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 size = oldArray.length;
if (size == 0) {
return new int[0];
}
for (int i = 0; i < oldArray.length; i++) {
if (oldArray[i] == 0) {
size--;
}
}
if (size == 0) {
return new int[0];
}
int[] noZero = new int[size];
for (int i = 0, j = 0; i < oldArray.length; i++) {
if (oldArray[i] != 0) {
noZero[j] = oldArray[i];
j++;
}
}
return noZero;
}
/**
* 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) {
if (array1.length == 0) {
return array2;
}
if (array2.length == 0) {
return array1;
}
int size = array1.length + array2.length;
int[] merged = new int[size];
int i=0,j=0,k=0;
while (i<array1.length&&j<array2.length) {
if (array1[i]<array2[j]) {
merged[k]=array1[i];
i++;
}
else if (array1[i]>array2[j]) {
merged[k]=array2[j];
j++;
}
else {
merged[k]=array1[i];
i++;
j++;
}
k++;
}
if (i==array1.length-1) {
System.arraycopy(array2, j, merged, k, array2.length-j);
k=k+array2.length-j;
}
if (i==array2.length-1) {
System.arraycopy(array1, i, merged, k, array1.length-i);
k=k+array1.length-i;
}
size = k;
int[] newArray = new int[size];
System.arraycopy(merged, 0, newArray, 0, size);
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 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 max) {
if (max == 1) {
return new int[0];
}
int[] fib = { 1, 1 };
int size = 2;
int capacity = 2;
int i = 1;
while (fib[i] < max) {
if (size == capacity) {
fib = grow(fib, capacity);
capacity = fib.length;
}
fib[i + 1] = fib[i - 1] + fib[i];
i++;
size++;
}
int[] newFib = new int[size-1];
System.arraycopy(fib, 0, newFib, 0, size-1);
return newFib;
}
/**
* 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[0];
}
int[] primes = new int[] { 2 };
if (max ==3) {
return primes;
}
int size = 1;
int capacity = 1;
int number = 3;
boolean prime = true;
while (primes[size - 1] < max) {
for (int i = 2; i < number; i++) {
if (number % i == 0) {
prime = false;
break;
}
}
if (prime == true) {
if (size == capacity) {
primes = grow(primes, capacity);
capacity = primes.length;
}
primes[size] = number;
size++;
}
number++;
prime = true;
}
int[] newPrimes = new int[size - 1];
System.arraycopy(primes, 0, newPrimes, 0, size-1);
return newPrimes;
}
/**
* 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 number = 2;
int size = 0;
int capacity = 10;
int[] perfectNumbers = new int[capacity];
while (number < max) {
int capa = 10;
int i = 0;
int[] factor = new int[capa];
int sum = 0;
for (int j = 1; j <= number / 2; j++) {
if (number % j == 0) {
if (i == capa) {
factor = grow(factor, capa);
capa = factor.length;
}
factor[i] = j;
sum += j;
i++;
}
}
if (sum == number && number != max) {
if (size == capacity) {
perfectNumbers = grow(perfectNumbers, capacity);
capacity = perfectNumbers.length;
}
perfectNumbers[size] = number;
size++;
}
number++;
}
int[] newPerfactNumber = new int[size];
System.arraycopy(perfectNumbers, 0, newPerfactNumber, 0, size);
return newPerfactNumber;
}
/**
* 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) {
StringBuffer stringBuffer = new StringBuffer();
for (int i = 0; i < array.length; i++) {
stringBuffer.append(array[i]);
if (i != array.length - 1) {
stringBuffer.append(seperator);
}
}
return stringBuffer.toString();
}
}