一些集合面试题

package com.fly;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class Test {

public static void main(String[] args) {
int[] a={3,5,6,7,2,3,32,12,34,5,256};

int[] b={1,2,3,4,5,6,7};

System.out.println(Arrays.toString(union(a,b)));

System.out.println(Arrays.toString(allin(a,b)));

System.out.println(Arrays.toString(minus(a,b)));

double[] da={1,2,3,4,5};
double[] db={1,1,1,1,1,1};
moving(da, db, 3);

moving2(da, db, 3);

}

public static Object[] union(int[] a1,int[] a2){
Set<Integer> set=new HashSet<Integer>();
for(int i=0;i<a1.length;i++){
set.add(a1[i]);
}
for(int j=0;j<a2.length;j++){
set.add(a2[j]);
}
return set.toArray();
}

public static Object[] allin(int[] a1,int[] a2){
Map<Integer,Boolean> map=new HashMap<Integer,Boolean>();
for(int i=0;i<a1.length;i++){
if(!map.containsKey(a1[i])){
map.put(a1[i], Boolean.FALSE);
}
}
for(int i=0;i<a2.length;i++){
if(map.containsKey(a2[i])){
map.put(a2[i], Boolean.TRUE);
}
}
List<Integer> list=new ArrayList<Integer>();
for(Iterator<Integer> i=map.keySet().iterator();i.hasNext();){
Integer a=i.next();
if(map.get(a)){
list.add(a);
}
}
return list.toArray();
}

public static Object[] minus(int[] a1,int[] a2){
List<Integer> list=new LinkedList<Integer>();
List<Integer> history=new LinkedList<Integer>();
for(int i=0;i<a1.length;i++){
if(!list.contains(a1[i])){
list.add(a1[i]);
}
}
for(int i=0;i<a2.length;i++){
if(list.contains(a2[i])){
history.add(a2[i]);
list.remove(a2[i]);
}else{
if(!history.contains(a2[i])){
list.add(a2[i]);
}
}
}

return list.toArray();
}

public static void moving(double[] a,double[] b,int k){
int n=a.length>b.length?b.length:a.length;
for(int i=0;i<n;i++){
int count=0;
double total=0;
for(int j=i;count<k&&j>=0;j--,count++){
total=total+a[j];
}
System.out.println("total--->"+total);
System.out.println("count--->"+count);
b[i]=total/count;
}
System.out.println(Arrays.toString(b));
}
public static void moving2(double[] a,double[] b,int k){
int n=a.length>b.length?b.length:a.length;
for(int i=0;i<n;i++){
int count=0;
double total=0;
if(i<k){
for(int j=i;count<k&&j>=0;j--,count++){
total=total+a[j];
}
System.out.println("total--->"+total);
System.out.println("count--->"+count);
b[i]=total/count;
}else{
b[i]=(b[i-1]*k+a[i]-a[i-k])/k;
}

}
System.out.println(Arrays.toString(b));
}
}