代码如下:
package com.hsx.ccf;
import java.util.Scanner;
public class Ccf20140301 {
public static void main(String[] args) {
@SuppressWarnings("resource")
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
int[] a = new int[501];
for(int i = 0; i < n; i++){
a[i] = scanner.nextInt();
}
//判断相反数及个数
int count = 0;
for(int i = 0; i < n; i++){
for(int j = i + 1; j < n; j++){
if(a[i]+a[j] == 0){
count++;
}
}
}
System.out.println(count);
}
}