BZOJ3155Preprefix sum

#include<bits/stdc++.h>
using namespace std;
#define MAXN 100001
typedef long long LL;
int n,m,a[MAXN];
LL delta[MAXN<<2],sum[MAXN<<2],S[MAXN];

void read(int &x,char ch=getchar())
{
    for (;ch<‘0‘ || ch>‘9‘;ch=getchar());
    for (x=0;ch>=‘0‘ && ch<=‘9‘;ch=getchar()) x=(x<<1)+(x<<3)+ch-‘0‘;
}

void build(int s,int l,int r)
{
    int mid=(l+r)/2;
    if (l==r) return sum[s]=(LL)S[l],void();
    build(s*2,l,mid),build(s*2+1,mid+1,r),sum[s]=sum[s*2]+sum[s*2+1];
}

void pushdown(int s,int l,int r)
{
    int mid=(l+r)/2;
    if (!delta[s]) return;
    sum[s*2]+=delta[s]*(LL)(mid-l+1),sum[s*2+1]+=delta[s]*(LL)(r-mid),delta[s*2]+=delta[s],delta[s*2+1]+=delta[s],delta[s]=0;
}

LL query(int s,int l,int r,int x,int y)
{
    int mid=(l+r)/2;
    LL ans=0;
    if (x<=l && y>=r) return sum[s];
    pushdown(s,l,r);
    if (x<=mid) ans+=query(s*2,l,mid,x,y);
    if (y>mid) ans+=query(s*2+1,mid+1,r,x,y);
    return ans;
}

void insert(int s,int l,int r,int x,int y,int z)
{
    int mid=(l+r)/2;
    if (x<=l && y>=r) return sum[s]+=(LL)z*(r-l+1),delta[s]+=(LL)z,void();
    pushdown(s,l,r);
    if (x<=mid) insert(s*2,l,mid,x,y,z);
    if (y>mid) insert(s*2+1,mid+1,r,x,y,z);
    sum[s]=sum[s*2]+sum[s*2+1];
}

int main()
{
    int i,x,y;
    char s[10];
    //freopen("3155.in","r",stdin),freopen("3155.out","w",stdout);
    read(n),read(m);
    for (i=1;i<=n;++i) read(a[i]),S[i]=S[i-1]+(LL)a[i];
    build(1,1,n);
    while (m--)
      {
          scanf("%s",s),read(x);
          if (s[0]==‘M‘) read(y),insert(1,1,n,x,n,y-a[x]),a[x]=y;
          else printf("%lld\n",query(1,1,n,1,x));
      }
    return 0;
}