问题描述：
有两个有序整数集合a和b，写一个函数找出它们的交集？
几种解决方案：
一：
import java.util.Arrays;
public class Test {
public static void main(String args[]){
int[] b = {4, 6, 7, 7, 7, 7, 8, 8, 9, 10, 100, 130, 130, 140, 150};
int[] a = {2, 3, 4, 4, 4, 4, 7, 8, 8, 8, 8, 9, 100, 130, 150, 160};
int[] c = intersect(a, b);
System.out.println(Arrays.toString(c));
}
public static int[] intersect(int[] a, int[] b) {
if(a[0] > b[b.length - 1] || b[0] > a[a.length - 1]) {
return new int[0];
}
int[] intersection = new int[Math.max(a.length, b.length)];
int offset = 0;
for(int i = 0, s = i; i < a.length && s < b.length; i++) {
while(a[i] > b[s]) {
s++;
}
if(a[i] == b[s]) {
intersection[offset++] = b[s++];
}
while(i < (a.length - 1) && a[i] == a[i + 1]) {
i++;
}
}
if(intersection.length == offset) {
return intersection;
}
int[] duplicate = new int[offset];
System.arraycopy(intersection, 0, duplicate, 0, offset);
return duplicate;
}
}
二：
import java.util.ArrayList;
public class jiaoji {
public static void main(String[] args) {
// TODO Auto-generated method stub
int[] b = { 4, 6, 7, 7, 7, 8, 8, 9, 10, 100, 130, 140, 150 };
int[] a = { 2, 3, 4, 4, 4, 7, 8, 8, 8, 8, 9, 100, 130, 150, 160 };
ArrayList c = sect(a, b);
for (int i = 0; i < c.size(); i++) {
System.out.print(c.get(i) + ",");
}
}
public static ArrayList sect(int[] a, int[] b) {
int k = 0;
int startposb = 0;
if (a[0] > b[b.length - 1] || b[0] > a[a.length - 1]) {
return new ArrayList();
}
ArrayList arraylist = new ArrayList();
for (int i = 0; i < a.length; i++) {
for (int j = startposb; j < b.length; j++) {
if (a[i] == b[j]) {
arraylist.add(k, a[i]);
k++;
startposb = j + 1;
break;
}
}
}
return arraylist;
}
}
三：
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
public class NumberCross {
public static void main(String[] args) {
int a[] = {1,3,4,5,6,7,499,199};
int b[] = {3,299,199,8,9,499};
Set<Integer> list = new HashSet<Integer>();
for(int i=0; i<a.length; i++) {
list.add(a[i]);
}
for(int j=0; j<b.length; j++) {
list.add(b[j]);
}
for(Iterator<Integer> iter=list.iterator(); iter.hasNext();) {
System.out.print(iter.next() + " ");
}
}
}
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