package com.github.eloiseSJTU.coding2017.array;
import java.security.InvalidParameterException;
import com.github.eloiseSJTU.coding2017.basic.ArrayList;
import com.github.eloiseSJTU.coding2017.basic.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
*/
public void reverseArray(int[] origin) {
if (origin == null) {
return;
}
int left = 0;
int right = origin.length - 1;
while (left < right) {
int tmp = origin[left];
origin[left] = origin[right];
origin[right] = tmp;
left++;
right--;
}
}
/**
* 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) {
return null;
}
int count = 0;
for (int i = 0; i < oldArray.length; i++) {
if (oldArray[i] != 0) {
count++;
}
}
int[] newArray = new int[count];
int index = 0;
for (int i = 0; i < oldArray.length; i++) {
if (oldArray[i] != 0) {
newArray[index++] = oldArray[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 int[] merge(int[] array1, int[] array2) {
if (array1 == null) {
return array2;
}
if (array2 == null) {
return array1;
}
int len1 = array1.length;
int len2 = array2.length;
ArrayList arrayList = new ArrayList();
int i = 0;
int j = 0;
while (i < len1 && j < len2) {
if (array1[i] < array2[j]) {
arrayList.add(array1[i]);
i++;
} else if (array1[i] > array2[j]) {
arrayList.add(array2[j]);
j++;
} else {
arrayList.add(array1[i]);
i++;
j++;
}
}
while (i < len1) {
arrayList.add(array1[i++]);
}
while (j < len2) {
arrayList.add(array2[j++]);
}
return toArray(arrayList);
}
/**
* 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 (oldArray == null) {
return null;
}
if (size < 0) {
throw new InvalidParameterException("size can't be negative");
}
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 int[] fibonacci(int max) {
if (max <= 1) {
return new int[0];
}
ArrayList arrayList = new ArrayList();
int a = 1;
arrayList.add(a);
int b = 1;
arrayList.add(b);
int c = a + b;
while (c < max) {
arrayList.add(c);
a = b;
b = c;
c = a + b;
}
return toArray(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 int[] getPrimes(int max) {
ArrayList arrayList = new ArrayList();
for (int i = 2; i < max; i++) {
boolean pn = true;
for (int j = 0; j < arrayList.size(); j++) {
if (i % (int) arrayList.get(j) == 0) {
pn = false;
break;
}
}
if (pn) {
arrayList.add(i);
}
}
return toArray(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 int[] getPerfectNumbers(int max) {
ArrayList arrayList = new ArrayList();
for (int i = 2; i < max; i++) {
int sum = 0;
for (int j = 1; j < i; j++) {
if (i % j == 0) {
sum += j;
}
}
if (sum == i) {
arrayList.add(i);
}
}
return toArray(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) {
if (array == null || array.length == 0) {
return "";
}
StringBuffer stringBuffer = new StringBuffer();
int i = 0;
for (; i < array.length - 1; i++) {
stringBuffer.append(array[i] + seperator);
}
stringBuffer.append(array[i]);
return stringBuffer.toString();
}
private int[] toArray(List list) {
int size = list.size();
int[] result = new int[size];
for (int i = 0; i < size; i++) {
result[i] = (int) list.get(i);
}
return result;
}
}