【nowcoder 牛客 13887】Maximize The Beautiful Value

Maximize The Beautiful Value

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題目大意

• 給定一個序列，序列價值爲：a[i] * i
• 有且僅有一次交換，將一個值提前最少k個，其他相對順序不變
• 求序列價值

解題思路

使用前綴和找到最小差值相減

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep2(i,st,ed) for(int i = st; i < ed; ++i)
#define mk(x,y) make_pair(x,y)
#define pb(x) push_back(x)
const ll mod = 1e9 + 7;
const ll N = 2e5 + 200;
const ll INF = 1e18;
const double eps = 1e-7;


int w[N], v[N];
ll dp[N];
int main(){
	int t;
	cin>>t;
	while(t--){
		ll n,k;
		cin>>n>>k;
		vector<ll> a(n+1, 0);
		vector<ll> b(n+1, 0);
		ll sum = 0;
		rep2(i,1,n+1){
			cin>>a[i];
			sum += i * a[i];
			b[i] = b[i-1] + a[i];
		}
		ll mi = -INF;
		// cout<<sum<<endl;
		rep2(i,k,n+1){
			ll tmp = b[i-1] - b[i-k-1] - a[i] * k;
			mi = max(mi, tmp);	
		}
		sum += mi;
		cout<<sum<<endl;
	}	

	return 0;
}