• Marvolo Gaunt's Ring CodeForces


    Professor Dumbledore is helping Harry destroy the Horcruxes. He went to Gaunt Shack as he suspected a Horcrux to be present there. He saw Marvolo Gaunt's Ring and identified it as a Horcrux. Although he destroyed it, he is still affected by its curse. Professor Snape is helping Dumbledore remove the curse. For this, he wants to give Dumbledore exactly x drops of the potion he made.

    Value of x is calculated as maximum of p·ai + q·aj + r·ak for given p, q, r and array a1, a2, ... an such that 1 ≤ i ≤ j ≤ k ≤ n. Help Snape find the value of x. Do note that the value of x may be negative.

    Input

    First line of input contains 4 integers n, p, q, r ( - 109 ≤ p, q, r ≤ 109, 1 ≤ n ≤ 105).

    Next line of input contains n space separated integers a1, a2, ... an ( - 109 ≤ ai ≤ 109).

    Output

    Output a single integer the maximum value of p·ai + q·aj + r·ak that can be obtained provided 1 ≤ i ≤ j ≤ k ≤ n.

    Example

    Input
    5 1 2 3
    1 2 3 4 5
    Output
    30
    Input
    5 1 2 -3
    -1 -2 -3 -4 -5
    Output
    12

    Note

    In the first sample case, we can take i = j = k = 5, thus making the answer as 1·5 + 2·5 + 3·5 = 30.

    In second sample case, selecting i = j = 1 and k = 5 gives the answer 12.

    题解:注意顺序是一定的,i<=j<=k,所以可以枚举中间值j,然后用两个数组分别存第一项的前缀最大值,第三项的后缀最大值,最后加起来遍历一遍就行了。

     1 #include<bits/stdc++.h>
     2 using namespace std;
     3 typedef long long ll;
     4 
     5 const int maxn=1e5+5;
     6 
     7 ll n,p,q,r;
     8 ll a[maxn],b[maxn],c[maxn];
     9 
    10 int main()
    11 {   cin>>n>>p>>q>>r;
    12     ll temp;
    13     for(int i=1;i<=n;i++){
    14         cin>>temp;
    15         a[i]=p*temp;
    16         b[i]=q*temp;
    17         c[i]=r*temp;
    18     }    
    19     temp=a[1];
    20     for(int i=1;i<=n;i++){
    21         temp=max(temp,a[i]);
    22         a[i]=temp;
    23     }
    24     temp=c[n];
    25     for(int i=n;i>=1;i--){
    26         temp=max(temp,c[i]);
    27         c[i]=temp;
    28     }
    29     temp=a[1]+b[1]+c[1];
    30     for(int i=1;i<=n;i++) temp=max(temp,a[i]+b[i]+c[i]);
    31     cout<<temp<<endl;
    32 }
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  • 原文地址:https://www.cnblogs.com/zgglj-com/p/7745426.html
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