CF276 C. Little Girl and Maximum Sum

题目传送门：https://codeforces.com/problemset/problem/276/C

题目大意：
给定一串长度为\(n\)的序列\(A\)，\(m\)个询问\((l_i,r_i)\)，记\(V_i=\sum\limits_{j=l_i}^{r_i}A_j\)

问，在对\(A\)序列任意排序后，所能得到\(\sum\limits_{i=1}^mV_i\)最大是多少

统计每个点被询问的次数，将大数尽可能填入询问次数多的位置即可

至于统计次数，就不需要数据结构了，差分即可

/*program from Wolfycz*/
#include
#include
#include
#include
#include
#include
#include
#define Fi first
#define Se second
#define ll_inf 1e18
#define MK make_pair
#define sqr(x) ((x)*(x))
#define pii pair
#define int_inf 0x7f7f7f7f
using namespace std;
typedef long long ll;
typedef unsigned int ui;
typedef unsigned long long ull;
inline char gc(){
	static char buf[1000000],*p1=buf,*p2=buf;
	return p1==p2&&(p2=(p1=buf)+fread(buf,1,1000000,stdin),p1==p2)?EOF:*p1++;
}
templateinline T frd(T x){
	int f=1; char ch=gc();
	for (;ch<'0'||ch>'9';ch=gc())	if (ch=='-')    f=-1;
	for (;ch>='0'&&ch<='9';ch=gc())	x=(x<<1)+(x<<3)+ch-'0';
	return x*f;
}
templateinline T read(T x){
	int f=1; char ch=getchar();
	for (;ch<'0'||ch>'9';ch=getchar())	if (ch=='-')	f=-1;
	for (;ch>='0'&&ch<='9';ch=getchar())	x=(x<<1)+(x<<3)+ch-'0';
	return x*f;
}
inline void print(int x){
	if (x<0)	putchar('-'),x=-x;
	if (x>9)	print(x/10);
	putchar(x%10+'0');
}
const int N=2e5;
int A[N+10],S[N+10];
int main(){
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);
	int n=read(0),m=read(0);
	for (int i=1;i<=n;i++)	A[i]=read(0);
	for (int i=1;i<=m;i++){
		int l=read(0),r=read(0);
		S[l]++,S[r+1]--;
	}
	for (int i=1;i<=n;i++)	S[i]+=S[i-1];
	sort(A+1,A+1+n);
	sort(S+1,S+1+n);
	ll Ans=0;
	for (int i=1;i<=n;i++)	Ans+=1ll*A[i]*S[i];
	printf("%lld\n",Ans);
	return 0;
}
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