如何用Java求两数组交集，并集，差集(整理的笔记)

package com.demo;

public class TestUnion {
    public static void main(String args[]){
        int a[] = {1,5,8,10,14,15,17,18,20,22,24,25,28};
        int b[] = {2,4,6,8,10,12};
//        for(int i = 0; i < b.length; i++){
//            for(int j = 0; j < a.length; j++){
//                if(b[i] == a[j]){
//                    System.out.print(" " + b[i]);
//                    break;
//                }
//                else
//                    continue;
//            }
//        }
        int i=0;
        int j=0;
        while(i<a.length && j < b.length)
        {
        if(a[i] < b[j])
        {
            i++;
        }
        else if (a[i] == b[j])
        {
          System.out.println(a[i]);
            i++;
            j++;
        }
        else
        {
            j++;
        }
        }
    }
}

 

如何求两个数组的交集，并集，差集

int[] arr1={1,2,3,4,5,6,7,8,9,10};

int[] arr2={2,4,6,8,10};

交集：
public class ArrayListTest{
public static void main(String[] args){
int[] arr1={1,2,3,4,5,6,7,8,9,10};
int[] arr2={2,4,6,8,10};
for(int i=0;i<arr1.length;i++){
for(int j=0;j<arr2.length;j++){
if(arr1[i]==arr2[j])
System.out.println(arr2[j]);
}
}
}
}

 

 

并集：
public class ArrayListTest{
public static void main(String[] args){
int[] arr1={1,2,3,4,5,6,7,8,9,10};
int[] arr2={2,4,6,8,10};
int[] arr3=new int[100];
int k=arr1.length;
int flag=0;
System.arraycopy(arr1, 0, arr3, 0, arr1.length);
for(int i=0;i<arr2.length;i++){
for(int j=0;j<arr1.length;j++){
if(arr2[i]==arr1[j]){
flag=1;
}
}
if(flag!=1){
arr3[k]=arr2[i];
k++;
}
flag=0;
}
for(int z=0;z<k;z++){
System.out.print(arr3[z]);
}
}
}

 

差集：
public class ArrayListTest{
public static void main(String[] args){
int[] arr1={1,2,3,4,5,6,7,8,9,10};
int[] arr2={2,4,6,8,10};
int[] arr3=new int[100];
int k=0;
int flag=0;
for(int i=0;i<arr1.length;i++){
for(int j=0;j<arr2.length;j++){
if(arr2[j]==arr1[i]){
flag=1;
}
}
if(flag!=1){
arr3[k]=arr1[i];
k++;
}
flag=0;
}
for(int z=0;z<k;z++){
System.out.print(arr3[z]);
}
}
}

评论

2 楼 nextw3 2011-05-24  

残念，代码写错了

1 楼 nextw3 2011-05-24  

//并集
public class ArrayListTest{
public static void main(String[] args){
int[] arr1={1,2,3,4,5,6,7,8,9,10};
int[] arr2={2,4,6,8,10};
int[] arr3=new int[100];
int k=arr1.length;
System.arraycopy(arr1, 0, arr3, 0, arr1.length);
for(int i=0;i<arr2.length;i++){
for(int j=0;j<arr1.length;j++){
if(arr2[i]==arr1[j]){
break;
}
arr3[k]=arr2[i];
k++;
}
}
for(int z=0;z<k;z++){
System.out.print(arr3[z]);
}
}
}

去掉flag变量，用break控制。这样不是更好吗？