loj #6277. 数列分块入门 1

分块第一题。。。

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=50005;
int belong[N],block,n,q,l[N],r[N],num;
ll a[N],s[N];
void build(){
    block=sqrt(n);
    num=n/block;if(n%block)++num;
    for(int i=1;i<=num;++i)l[i]=(i-1)*block+1,r[i]=i*block;
    r[num]=n;
    for(int i=1;i<=n;++i)belong[i]=(i-1)/block+1;
}
ll ask(int x){
    return a[x]+s[belong[x]];
}
void update(int x,int y,ll add){
    if(belong[x]==belong[y]){
        for(int i=x;i<=y;++i)a[i]+=add;
        return ;
    }
    for(int i=x;i<=r[belong[x]];++i)a[i]+=add;
    for(int i=belong[x]+1;i<belong[y];++i)s[i]+=add;
    for(int i=l[belong[y]];i<=y;++i)a[i]+=add;
    return ;
}
int main(){
    scanf("%d",&n);
    for(int i=1;i<=n;++i)scanf("%d",&a[i]);
    build();
    for(int i=1;i<=n;++i){
        int opt,l,r;
        ll c;
        scanf("%d%d%d%lld",&opt,&l,&r,&c);
        if(opt==1){
            printf("%d\n",ask(r));
        }
        else{
            update(l,r,c);
        }
    }
    return 0;
}