电位计 (Potentiometers,Dhaka 2006,LA 2191)

#include <iostream>
#include <string.h>
#include <string>
#include <fstream>
#include <algorithm>
#include <stdio.h>
#include <vector>
#include <queue>
#include <set>
#include <cmath>
using namespace std;
const double eps = 1e-8;
const double pi=acos(-1.0);
const int INF=0x7fffffff;
unsigned long long uINF = ~0LL;
#define MAXN 200007
#define mod 1000000007
typedef long long LL;
int C[MAXN],a[MAXN],n,T=1,x,y;
int lowbit(int x)
{
    return x&-x;
}
int sum(int x)
{
    int ret=0;
    while(x>0)
    {
        ret+=C[x];x-=lowbit(x);
    }
    return ret;
}
void add(int x,int d)
{
    while(x<=n){
    C[x]+=d;x+=lowbit(x);}
}

int main()
{

    while(scanf("%d",&n),n!=0)
    {
        if(T>1)printf("
");
        printf("Case %d:
",T++);
        memset(a,0,sizeof(a));
        memset(C,0,sizeof(C));
        for(int i=1;i<=n;i++)
        {scanf("%d",&a[i]);add(i,a[i]);}
        string t;
        while(cin>>t,t!="END")
        {
            if(t=="M"){
                scanf("%d%d",&x,&y);
                printf("%d
",sum(y)-sum(x-1));
            }
            else if(t=="S"){
                scanf("%d%d",&x,&y);
                add(x,y-a[x]);
                a[x]=y;

            }

        }
    }
    return 0;
}

树状数组