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可以先看一下LG P4868 Preprefix sum,很经典一道题,维护一下后缀和就可以了

这题的话就是把上面那道题变了一下

由于值域太大,我们可以使用 动态开点线段树 或 树状数组+离散化

#include<bits/stdc++.h>
namespace ZDY{
    #pragma GCC optimize(3)
    #define il __inline__ __attribute__ ((always_inline))
    #define register
    #define ll long long
    #define ull unsigned long long
    #define db double
    #define sht short
    #define MB template <class T>il
    #define Fur(i,x,y) for(int i(x);i<=y;++i)
    #define Fdr(i,x,y) for(int i(x);i>=y;--i)
    #define fl(i,x) for(int i(head[x]),to;to=e[i].to,i;i=e[i].nxt)
    #define clr(x,y) memset(x,y,sizeof(x))
    #define cpy(x,y) memcpy(x,y,sizeof(x))
    #define fin(s) freopen(s".in","r",stdin)
    #define fout(s) freopen(s".out","w",stdout)
    #define fcin ios::sync_with_stdio(false)
    #define l2(n) ((int)(log2(n)))
    #define inf 2122219134
    MB T ABS(T x){return x>0?x:-x;}
    MB T MAX(T x,T y){return x>y?x:y;}
    MB T MIN(T x,T y){return x<y?x:y;}
    MB T GCD(T x,T y){return y?GCD(y,x%y):x;}
    MB void SWAP(T &x,T &y){T t=x;x=y;y=t;}
}using namespace ZDY;using namespace std;
namespace IO{const int str=1<<20;static char in_buf[str],*in_s,*in_t;bool __=0;il char gc(){return (in_s==in_t)&&(in_t=(in_s=in_buf)+fread(in_buf,1,str,stdin)),in_s==in_t?EOF:*in_s++;}il void in(string &ch){ch.clear();if(__)return;char c;while((c=gc())!=EOF&&isspace(c));if(c==EOF){__=1;return;}ch+=c;while((c=gc())!=EOF&&!isspace(c))ch+=c;if(c==EOF)__=1;}il void in(char &ch){if(__)return;char c;while((c=gc())!=EOF&&isspace(c));if(c==EOF)__=1;else ch=c;}il void in(char *ch){*ch='\0';if(__)return;char c;while((c=gc())!=EOF&&isspace(c));if(c==EOF){__=1;return;}*ch=c;ch++;while((c=gc())!=EOF&&!isspace(c))*ch=c,ch++;if(c==EOF)__=1;*ch='\0';}template<typename T>il void in(T &x){if(__)return;char c=gc();bool f=0;while(c!=EOF&&(c<'0'||c>'9'))f^=(c=='-'),c=gc();if(c==EOF){__=1;return;}x=0;while(c!=EOF&&'0'<=c&&c<='9')x=x*10+c-48,c=gc();if(c==EOF)__=1;if(f)x=-x;}template<typename T,typename ... arr>il void in(T &x,arr & ... y){in(x),in(y...);}const char ln='\n';static char out_buf[str],*out_s=out_buf,*out_t=out_buf+str;il void flush(){fwrite(out_buf,1,out_s-out_buf,stdout);out_s=out_buf;}il void pt(char c){(out_s==out_t)?(fwrite(out_s=out_buf,1,str,stdout),*out_s++=c):(*out_s++=c);}il void out(const char* s){while(*s)pt(*s++);}il void out(char* s){while(*s)pt(*s++);}il void out(char c){pt(c);}il void out(string s){for(int i=0;s[i];i++)pt(s[i]);}template<typename T>il void out(T x){if(!x){pt('0');return;}if(x<0)pt('-'),x=-x;char a[50],t=0;while(x)a[t++]=x%10,x/= 10;while(t--)pt(a[t]+'0');}template<typename T,typename ... arr>il void out(T x,arr & ... y){out(x),out(y...);}}using namespace IO;
#define N 100011
int n,ls[N*20],rs[N*20],sz=1;
ll s[N*20],ps[N*20];
#define pu s[x]=s[ls[x]]+s[rs[x]],ps[x]=ps[ls[x]]+ps[rs[x]]
void add(int p,int v,int l=0,int r=INT_MAX,int x=1){
    if(l==r){
        s[x]+=v;
        ps[x]+=1ll*v*(INT_MAX-p+1);
        return;
    }
    int m=(l+r)>>1;
    if(p<=m)add(p,v,l,m,ls[x]?ls[x]:ls[x]=++sz);
    else add(p,v,m+1,r,rs[x]?rs[x]:rs[x]=++sz);
    pu;
}
ll ask(int p,int l=0,int r=INT_MAX,int x=1){
    if(r<=p)return ps[x]-s[x]*(INT_MAX-p);
    int m=(l+r)>>1;
    return ask(p,l,m,ls[x])+((p>m)?ask(p,m+1,r,rs[x]):0);
}
int main(){
    int q;
    in(n,q);
    int opt,x,y;
    Fur(i,1,n){
        in(x,y);
        add(x,y);
    }
    while(q--){
        in(opt,x,y);
        if(opt==1){
            db ans=(long db)(ask(y)-ask(x-1))/(long db)(y-x+1);
            printf("%.4f\n",ans);
        }
        else add(x,y);
    }
}
LG 4915 帕秋莉的魔导书
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