[HDU 1166] 敌兵布阵

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1166
一个线段树区间求和的模板题了。
  1 #include<iostream>
  2 #include<cstdio>
  3 #include<cstring>
  4 using namespace std;
  5 
  6 #define MID(l,r) (l+r)>>1
  7 #define lson root<<1
  8 #define rson root<<1|1
  9 
 10 const int maxn=5e4+5;
 11 struct Tree
 12 {
 13     int l,r;
 14     int sum;
 15 }tree[maxn*3];
 16 
 17 int arr[maxn],ans;
 18 
 19 void Build(int root,int l,int r)
 20 {
 21     tree[root].l=l;
 22     tree[root].r=r;
 23     if(l==r)
 24         tree[root].sum=arr[l];
 25     else
 26     {
 27         int mid=MID(l,r);
 28         Build(lson,l,mid);
 29         Build(rson,mid+1,r);
 30         tree[root].sum=tree[lson].sum+tree[rson].sum;
 31     }
 32 }
 33 
 34 void Query(int root,int x,int y)
 35 {
 36     if(x<=tree[root].l&&y>=tree[root].r)
 37         ans+=tree[root].sum;
 38     else
 39     {
 40         int mid=MID(tree[root].l,tree[root].r);
 41         if(x>mid)
 42         {
 43             Query(rson,x,y);
 44         }
 45         else if(y<=mid)
 46         {
 47             Query(lson,x,y);
 48         }
 49         else
 50         {
 51             Query(lson,x,y);
 52             Query(rson,x,y);
 53         }
 54     }
 55 }
 56 
 57 void Update(int root,int x,int y)
 58 {
 59     tree[root].sum+=y;
 60     if(tree[root].l==x&&tree[root].r==x)
 61         return ;
 62     int mid=MID(tree[root].l,tree[root].r);
 63     if(x>mid)
 64         Update(rson,x,y);
 65     else
 66         Update(lson,x,y);
 67 
 68 }
 69 
 70 int main()
 71 {
 72     int T;
 73     cin>>T;
 74     for(int flag=1;flag<=T;flag++)
 75     {
 76         int n;
 77         cin>>n;
 78         for(int i=1;i<=n;i++)
 79             scanf("%d",&arr[i]);
 80         Build(1,1,n);
 81         printf("Case %d:
",flag);
 82         char s[10];
 83         while(scanf("%s",s)!=EOF)
 84         {
 85             if(strcmp(s,"End")==0)
 86                 break;
 87             else if(strcmp(s,"Add")==0)
 88             {
 89                 int x,y;
 90                 scanf("%d%d",&x,&y);
 91                 Update(1,x,y);
 92             }
 93             else if(strcmp(s,"Sub")==0)
 94             {
 95                 int x,y;
 96                 scanf("%d%d",&x,&y);
 97                 Update(1,x,-y);
 98             }
 99             else if(strcmp(s,"Query")==0)
100             {
101                 int x,y;
102                 scanf("%d%d",&x,&y);
103                 ans=0;
104                 Query(1,x,y);
105                 printf("%d
",ans);
106             }
107         }
108     }
109     return 0;
110 }