cf455A boredom

标签：turn   set   ++   play   class   game   contain   i+1   tle   

Alex doesn‘t like boredom. That‘s why whenever he gets bored, he comes up with games. One long winter evening he came up with a game and decided to play it.

Given a sequence a consisting of n integers. The player can make several steps. In a single step he can choose an element of the sequence (let‘s denote it a_k) and delete it, at that all elements equal to a_k + 1and a_k - 1 also must be deleted from the sequence. That step brings a_k points to the player.

Alex is a perfectionist, so he decided to get as many points as possible. Help him.

Input

The first line contains integer n (1 ≤ n ≤ 10⁵) that shows how many numbers are in Alex‘s sequence.

The second line contains n integers a₁, a₂, ..., a_n (1 ≤ a_i ≤ 10⁵).

Output

Print a single integer — the maximum number of points that Alex can earn.

Examples

2
1 2

2

3
1 2 3

4

9
1 2 1 3 2 2 2 2 3

10

Note

Consider the third test example. At first step we need to choose any element equal to 2. After that step our sequence looks like this [2, 2, 2, 2]. Then we do 4 steps, on each step we choose any element equals to 2. In total we earn 10 points.

思路：dp。就是表示每一步dp的状态，即此步状态可能是前一步dp[i-1]的状态（即这一步的数已被消除），或者是前两步dp[i-2]的状态加上这一步的值（因为下一步的状态不确定，所以下一步的值不能消去）。

所以状态转移方程就是dp[i] = max(dp[i-2] + a[i]*i,dp[i-1]);

#include<bits/stdc++.h>
using namespace std;
const int N = 1e5+10;
typedef long long ll;
ll a[N],dp[N];
int main()
{
    int n,x,ma = 0,mi = N;
    memset(a,0,sizeof(a));
    memset(dp,0,sizeof(dp));
    cin>>n;
    for(ll i = 0; i < n; i++) {
        scanf("%d",&x);
        a[x]++;
        if(x > ma) {
            ma = x;
        }
        if(x < mi) {
            mi = x;
        }
    }
    dp[mi] = a[mi]*mi;
    for(ll i = mi+1; i <= ma; i++) {
        dp[i] = max(dp[i-2]+a[i]*i,dp[i-1]);
    }
    cout<<dp[ma]<<endl;
    return 0;
}

cf455A boredom

标签：turn   set   ++   play   class   game   contain   i+1   tle   

原文地址：https://www.cnblogs.com/clb123/p/11853280.html