树状数组再理解

#include 
#include 
#include 
#include 
#include 
#include 
#include
#include
#include
#include
#include
#include
#include
using namespace std;
const int maxn=80023;
int n,m,t;
long long int c[maxn];
int lobit(int x)
{return x&(-x);
}
void update(int pos,int k)
{while(pos<=n){c[pos]+=k;pos+=lobit(pos);}
}
int sum(int pos)
{int res=0;while(pos>0){res+=c[pos];pos-=lobit(pos);}return res;
}
int main()
{int i,j,ce=0,a1,a2;char ch[20];scanf("%d",&t);while(t--){memset(c,0,sizeof(c));ce++;//printf("Case %d:\n",ce);scanf("%d",&n);for(i=1;i<=n;i++){scanf("%d",&a1);update(i,a1);}printf("Case %d:\n",ce);while(1){scanf("%s",ch);if(ch[0]=='Q'){scanf("%d%d",&a1,&a2);printf("%d\n",sum(a2)-sum(a1-1));}else if(ch[0]=='S'){scanf("%d%d",&a1,&a2);update(a1,-a2);}else if(ch[0]=='A'){scanf("%d%d",&a1,&a2);update(a1,a2);}else{break;}}}return 0;
}