package basic.dataStructure;
/**
* @author : 温友朝
* @date : 2017/4/5
*/
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) {
int length = origin.length;
int[] reversed = new int[length];
for (int i = length - 1; i >= 0; i--) {
reversed[length - i - 1] = origin[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) {
int length = oldArray.length;
int[] arr = new int[length];
int index = 0;
for (int i = 0; i < length; i++) {
if (oldArray[i] != 0) {
arr[index] = oldArray[i];
index++;
}
}
//非0的数据个数
int[] newArr = new int[index];
System.arraycopy(arr, 0, newArr, 0, index);
return newArr;
}
public static Object[] remove(Object[] oldArray, Object value){
int length = oldArray.length;
Object[] arr = new Object[length];
int index = 0;
for (int i = 0; i < length; i++) {
if (oldArray[i] != value) {
arr[index] = oldArray[i];
index++;
}
}
Object[] newArr = new Object[index];
System.arraycopy(arr, 0, newArr, 0, index);
return newArr;
}
/**
* 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 length1 = array1.length;
int length2 = array2.length;
int[] arr = new int[length1 + length2];
System.arraycopy(array1, 0, arr, 0, length1);
System.arraycopy(array2, 0, arr, length1, length2);
//去重
for(int i = 0; i < arr.length; i++){
for(int j = 0; j < arr.length; j++){
if(i != j && arr[i] == arr[j]){
arr[j] = 0;
}
}
}
int[] data = removeZero(arr);
int length = data.length;
//排序
for (int i = 0; i < length; i++) {
for(int j = 0; j < length; j++){
if(data[i] < data[j]){
int tmp = data[i];
data[i] = data[j];
data[j] = tmp;
}
}
}
return data;
}
/**
* 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[] arr = new int[oldArray.length + size];
System.arraycopy(oldArray, 0, arr, 0, oldArray.length);
return arr;
}
/**
* 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 []
* F(0)=0,F(1)=1, F(n)=F(n-1)+F(n-2)(n>=2,n∈N*)
* @param max
* @return
*/
public int[] fibonacci(int max) {
int[] empty = {};
int[] arr2 = {1, 1};
switch (max){
case 0 : return empty;
case 1 : return empty;
case 2 : return arr2;
default: {
int[] data = arr2;
int d = data[0] + data[1];
while (d < max){
int length = data.length;
d = data[length - 1] + data[length - 2];
if(d > max){
return data;
}
int[] temp = new int[data.length + 1];
System.arraycopy(data, 0, temp, 0, length);
temp[length] = d;
data = temp;
}
}
}
return null;
}
/**
* 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) {
int[] data = new int[max];
int index = 0;
for(int i = 1; i < max; i++){
int divided = 0;
for(int j = i; j >= 1; j--){
if(i % j == 0){
divided++;
}
if(divided > 2){
break;
}else if(j == 1 && divided == 2){
data[index] = i;
index ++;
}
}
}
int[] result = new int[index];
System.arraycopy(data, 0, result, 0, index);
return result;
}
/**
* 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[] perfd = new int[max];
int perfIndex = 0;
for(int i = 1; i <= max; i++){
int index = 0;
int[] data = new int[i];
for(int j = i - 1; j >= 1; j--){
if(i % j == 0){
data[index] = j;
index ++;
}
if(j == 1 && getSum(data) == i){
perfd[perfIndex] = i;
perfIndex++;
}
}
}
return removeZero(perfd);
}
private int getSum(int[] arr){
int sum = 0;
for(int i : arr){
sum += i;
}
return sum;
}
/**
* 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 seperator
* @return
*/
public String join(int[] array, String seperator) {
StringBuffer sb = new StringBuffer();
for(int i : array){
sb.append(i).append(seperator);
}
return sb.substring(0, sb.length() - 1).toString();
}
}