D e s c r i p t i o n Description Description
I n p u t Input Input
O u t p u t Output Output
S a m p l e Sample Sample I n p u t Input Input#1
2 1 1 1
5 3
S a m p l e Sample Sample I n p u t Input Input#1
2 2 0 0
5 2
S a m p l e Sample Sample O u t p u t Output Output#1
21
S a m p l e Sample Sample O u t p u t Output Output#2
0
H i n t Hint Hint
T r a i n Train Train o f of of T h o u g h t Thought Thought
其实只用排个序
然后 A n s = ( ∑ x 1 A [ i ] ) ∗ 3 m + ( ∑ x + y x + 1 A [ i ] ) ∗ 2 m Ans = (\sum^{1}_{x}A[i]) * 3 ^ m + (\sum^{x + 1}_{x + y}A[i]) * 2 ^ m Ans=(∑x1A[i])∗3m+(∑x+yx+1A[i])∗2m
如果m == 1
再加上 ( ∑ n x + y + 1 A [ i ] ) (\sum^{x+y+1}_{n}A[i]) (∑nx+y+1A[i])
因为前x个肯定是贡献最大的,所以x个名额直接给前x个就行了
双倍的也是一样
所以直接x + 1到x + y的和乘上2 ^ m就行了
记得如果m等于1的时候
要把剩下的加上
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#define ll long long
//#define mod 1e9+7
using namespace std;
const int mod = 1e9 + 7;
int n, m, Sum, l, r, x, y;
int A[100005];
int power(int a,int b)
{
int Ans = 1;
a = a % mod;
while(b)
{
if(b & 1) Ans = (ll) Ans * a % mod;
a = (ll)a * a % mod;
b >>= 1;
}
return Ans;
}
bool nm(int i, int j)
{
return i > j;}
int main()
{
scanf("%d%d%d%d", &n, &m, &l, &r);
for(int i = 1; i <= n; ++i)
scanf("%d", &A[i]);
sort(A + 1, A + n + 1, nm);
x = power(3, m), y = power(2, m);
for(int i = 1; i <= l; ++i)
Sum = ((ll)Sum + A[i] * x) % mod;
for(int i = l + 1; i <= l + r; ++i)
Sum = ((ll)Sum + A[i] * y) % mod;
if(m == 1)
{
for(int i = l + r + 1; i <= n; ++i)
Sum = ((ll)Sum + A[i]) % mod;
}
printf("%d", Sum);
return 0;
}