Codeforces Round #260 (Div. 2) C. Boredom

统计每个数字出现的次数，然后从前往后dp;

其中dp[i][0]表示到第i个为止并且选择第i个能得到的最大值；

dp[i][1] 表示到第i个为止并且不选择第i个能得到的最大值；

最终结果取max(dp[manx][0],dp[maxn][1]);

#include<cstdio>
#include<cstring>
#include<cmath>
#include<climits>
#include<cctype>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#include<queue>
#include<vector>
#include<map>
#include<set>
#include<string>
#include<stack>
#define ll __int64
#define MAX 100010
#define INF INT_MAX
#define eps 1e-8

using namespace std;

ll a[MAX],dp[MAX][2];

int main(){
ll n;
while (scanf("%I64d",&n) != EOF){
memset(a,0,sizeof(a));
ll t,maxn = 0; http://codeforces.com/contests/455,456for (int i = 0; i<n; i++){
scanf("%I64d",&t);
maxn = max(maxn,t);
a[t]++;
}
memset(dp,0,sizeof(dp));
for (int i=1; i<=maxn; i++){
if (a[i] == 0){
dp[i][0] = max(dp[i-1][0],dp[i-1][1]);
dp[i][1] = max(dp[i-1][0],dp[i-1][1]);
continue;
}
if (a[i-1] == 0){
dp[i][0] = max(dp[i-1][0],dp[i-1][1]) + a[i]*i;
dp[i][1] = max(dp[i-1][0],dp[i-1][1]);
continue;
}
dp[i][0] = dp[i-1][1] + a[i]*i;
dp[i][1] = max(dp[i-1][0],dp[i-1][1]);
}
printf("%I64d\n",max(dp[maxn][0],dp[maxn][1]));
}
return 0;
}