hdu 1166 敌兵布阵

线段树的经典入门题：

#include<stdio.h>
struct node
{
  int l;
  int r;
  int val;
};
node tree[1000002];
int a[50010];
char oper[9];
int n;

void build(int i,int l,int r)
{
     tree[i].l=l;
     tree[i].r=r;
     tree[i].val=0;
     if(tree[i].l==tree[i].r)
     {
        tree[i].val=a[l];
        return;
     }
     int mid=(l+r)/2;
     build(2*i,l,mid);
     build(2*i+1,mid+1,r);
     tree[i].val=tree[2*i].val+tree[2*i+1].val;
}

int qurry(int i,int t,int k)
{
    if(tree[i].l==t&&tree[i].r==k)
    {
       return tree[i].val;
    }
    int mid=(tree[i].l+tree[i].r)/2;
    if(mid>=k)  return qurry(2*i,t,k);
    else if (t>mid) return qurry(2*i+1,t,k);
    else return (qurry(2*i,t,mid)+qurry(2*i+1,mid+1,k));
}
void updata(int i,int t,int add)
{
    if(tree[i].l==tree[i].r&&tree[i].r==t)
    {
       tree[i].val+=add;
       return;
    }
    int mid=(tree[i].l+tree[i].r)/2;
    if(mid>=t)  updata(2*i,t,add);
    else        updata(2*i+1,t,add);
    tree[i].val=tree[2*i].val+tree[2*i+1].val;
}

int main()
{
   int cas=0;
   int x,y;
   int test;
   scanf("%d",&test);
   while(test--)
   {
     cas++;
     scanf("%d",&n);
     for(int i=1;i<=n;i++)
     {
        scanf("%d",&a[i]);
     }
     build(1,1,n);
     printf("Case %d:\n",cas);
     while(scanf("%s",oper))
     {
       if(oper[0]=='Q')
       {
          scanf("%d%d",&x,&y);
          int ans=qurry(1,x,y);
          printf("%d\n",ans);
          continue;
       }
       else if(oper[0]=='A')
       {
          scanf("%d%d",&x,&y);
          updata(1,x,y);
          continue;
       }
       else if(oper[0]=='S')
       {
          scanf("%d%d",&x,&y);
          updata(1,x,-1*y);
          continue;
       }
       else
       {           break;
       }
     }
       }
return 0;
}