题目传送门
1 /*
2 题意：选择a[k]然后a[k]-1和a[k]+1的全部删除，得到点数a[k]，问最大点数
3 DP：状态转移方程：dp[i] = max (dp[i-1], dp[i-2] + (ll) i * cnt[i]);
4 只和x-1，x-2有关，和顺序无关，x-1不取，x-2取那么累加相同的值，ans = dp[mx]
5 */
6 #include <cstdio>
7 #include <algorithm>
8 #include <cstring>
9 #include <iostream>
10 #include <cmath>
11 using namespace std;
12
13 typedef long long ll;
14 const int MAXN = 1e5 + 10;
15 const int INF = 0x3f3f3f3f;
16 ll dp[MAXN];
17 int cnt[MAXN];
18
19 int main(void) //Codeforces Round #260 (Div. 1) A. Boredom
20 {
21 int n;
22 while (scanf ("%d", &n) == 1)
23 {
24 memset (dp, 0, sizeof (dp));
25 memset (cnt, 0, sizeof (cnt));
26
27 int x, mx = 0;
28 for (int i=1; i<=n; ++i) {scanf ("%d", &x); cnt[x]++; if (mx < x) mx = x;}
29
30 dp[1] = cnt[1];
31 for (int i=2; i<=mx; ++i)
32 {
33 dp[i] = max (dp[i-1], dp[i-2] + (ll) i * cnt[i]);
34 }
35
36 printf ("%I64d
", dp[mx]);
37 }
38
39 return 0;
40 }
41
42
43
44 /*
45 2
46 1 2
47 3
48 1 2 3
49 9
50 1 2 1 3 2 2 2 2 3
51 */