历史研究

题目大意

分块大法好

[code]#include<cstdio>
#include<algorithm>
#include<cmath>
#define fo(i,a,b) for(i=a;i<=b;i++)
#define fd(i,a,b) for(i=a;i>=b;i--)
using namespace std;
typedef long long ll;
const int maxn=100000+10;
int cnt[maxn],a[maxn],b[maxn],sum[1000][maxn];
ll ans[1000][1000];
int i,j,k,l,r,n,m,c;
ll t;
int main(){
    scanf("%d%d",&n,&m);
    fo(i,1,n) scanf("%d",&a[i]),b[i]=a[i];
    sort(b+1,b+n+1);
    l=unique(b+1,b+n+1)-b-1;
    fo(i,1,n) a[i]=lower_bound(b+1,b+l+1,a[i])-b;
    c=floor(sqrt(n))+1;
    fo(i,1,(n-1)/c+1){
        t=0;
        fo(j,(i-1)*c+1,n){
            cnt[a[j]]++;
            t=max(t,(ll)cnt[a[j]]*b[a[j]]);
            ans[i][(j-1)/c+1]=t;
        }
        fo(j,(i-1)*c+1,n) cnt[a[j]]--;
    }
    fo(i,1,(n-1)/c+1){
        fo(j,1,n) sum[i][j]=sum[i-1][j];
        fo(j,(i-1)*c+1,min(i*c,n)) sum[i][a[j]]++;
    }
    while (m--){
        scanf("%d%d",&j,&k);
        l=(j-1)/c+1;r=(k-1)/c+1;
        if (l==r){
            t=0;
            fo(i,j,k){
                cnt[a[i]]++;
                t=max(t,(ll)cnt[a[i]]*b[a[i]]);
            }
            fo(i,j,k) cnt[a[i]]--;
            printf("%lld\n",t);
            continue;
        }
        t=0;
        if (l+1<r) t=ans[l+1][r-1];
        fo(i,j,l*c) cnt[a[i]]++;
        fo(i,(r-1)*c+1,k) cnt[a[i]]++;
        fo(i,j,l*c){
            if (!cnt[a[i]]) continue;
            ll x=sum[r-1][a[i]]-sum[l][a[i]]+cnt[a[i]];
            x=(ll)x*b[a[i]];
            t=max(t,x);
            cnt[a[i]]=0;
        }
        fo(i,(r-1)*c+1,k){
            if (!cnt[a[i]]) continue;
            ll x=sum[r-1][a[i]]-sum[l][a[i]]+cnt[a[i]];
            x=(ll)x*b[a[i]];
            t=max(t,x);
            cnt[a[i]]=0;
        }
        printf("%lld\n",t);
    }
}