B. BerSU Ball

 

http://codeforces.com/contest/489/problem/B

 

二分匹配模板题

 

 

 1 public class Main {
 2     static final int maxn = 2000;
 3     static int n, m;
 4     static int[] a = new int[maxn];
 5     static int[] b = new int[maxn];
 6     static int[] c = new int[maxn];
 7     static int[] vis = new int[maxn];
 8 
 9     public static void main(String[] args) {
10         Scanner io = new Scanner(System.in);
11         n = io.nextInt();
12         for (int i = 0; i < n; i++) a[i] = io.nextInt();
13 
14         m = io.nextInt();
15         Arrays.fill(c, -1);
16         int ans = 0;
17         for (int i = 0; i < m; i++) b[i] = io.nextInt();
18         for (int i = 0; i < n; i++) {
19             Arrays.fill(vis, 0);
20             match(i);
21         }
22         for (int i = 0; i < m; i++) if (c[i] != -1) ans++;
23         System.out.println(ans);
24     }
25 
26     static boolean match(int i) {
27         //递归不走回头路，针对的是自己这一列，所以放在最前面
28         if (vis[i] == 1) return false;
29         vis[i] = 1;
30         for (int j = 0; j < m; j++) {
31             if (Math.abs(b[j] - a[i]) <= 1 && (c[j] == -1 || match(c[j]))) {
32                 c[j] = i;
33                 return true;
34             }
35         }
36         return false;
37     }
38 }