题目：

Sum

Time Limit: 9000 MS Memory Limit: 65536 K

Sum

Mr. Jojer is given n numbers and an extra integer x, he wants to know whether there are two numbers whose sum is x.

Input

The input file contains several test cases. The first line of each test case contains two integers, n(<=1000001) and x. From the next line of each test case, there are n numbers.

Output

Each test case corresponds to a line in the output, which is either "YES" if there exists an answer or "NO" if not.

Sample Input

3 3
1 2 3
2 3
1 3

Sample Output

YES
NO

解题代码：

import java.util.*;</p> <p>public class Main {<br /> public static void main(String[] args) {<br /> Scanner sc = new Scanner(System.in);<br /> int n, sum;<br /> int num;<br /> int[] hash = new int[65537];<br /> boolean flag;<br /> while(sc.hasNextInt()) {<br /> n = sc.nextInt();<br /> sum = sc.nextInt();<br /> flag = true;<br /> for(int i=0; i<n; i++) {<br /> num = sc.nextInt();<br /> hash[num] = 1;<br /> }<br /> for(int i=0; i<hash.length/2+1; i++) {<br /> if(hash[i]==1 && hash[sum-i]==1) {<br /> System.out.println("YES");<br /> flag = false;<br /> break;<br /> }<br /> }<br /> if(flag) {<br /> System.out.println("NO");<br /> }<br /> }<br /> }<br /> }<br />

用空间换取时间