牛客-Maximize The Beautiful Value

https://ac.nowcoder.com/acm/contest/5086/A

Generally meaning of problems: there is an array a [i], is calculated as Σa [i] * i, the subject requires a [i + k] Previous switched to position i, and a [i] to a [i + k -1] next move a unit, and recalculated, looking for the maximum sum.

Ideas: In the beginning of the direct violence, but each time plus it will time out. (And violence) and so the use of a prefix, the prefix, and to use and demand interval, that is, from a [i] to a [i + k-1] interval and, Σa and the beginning of [i] * i, then and changed and stored calculation    t = max (t, ans + a [i + k] * ia [i + k] * (i + k) + sum [i + k-1] -sum [i-1])

In summary, it is a prefix and numerous visits to optimize the use, can effectively solve the complex problem of too large.

The following is the AC codes:

 

#include<iostream>
#include<cstdio>
#include<algorithm> 
#include<cstring>
using namespace std;
long long sum[100100],a[100100];
int main(){
    int t;
    scanf("%d",&t);
    while(t--){
        long long n,k,ans=0;
        memset(sum,0,sizeof(sum));
        scanf(" %lld%lld",&n,&k);
        for(int i=1;i<=n;i++){
            scanf(" %lld",&a[i]);
            sum[i]+=sum[i-1]+a[i];
            ans+=a[i]*i; 
        }
        long long t=-1;
        for(int i=1;i<=n-k;i++){
            t=max(t,ans+a[i+k]*i-a[i+k]*(i+k)+sum[i+k-1]-sum[i-1]);
        }
        printf("%lld\n",t);
    }
    return 0;
}