HDU 1166 enemy army deployment

Analysis: line Segment tree templates, drawing analysis when learning, try not to look at others' templates, analyze them by yourself, understand the principles, and then write it out with a sense of accomplishment, that is, creating and updating. and query operations,

 #include<stdio.h>  #define N 50005  struct node{      int l,r;      int sum;  }tree[N<<2];  int a[N];  int ans,n;  void create(int x,int l,int r){      tree[x].l=l;      tree[x].r=r;      if(l==r){          tree[x].sum=a[l];          return;      }      int mid=(l+r)/2;      create(x*2,l,mid);      create(x*2+1,mid+1,r);      tree[x].sum=tree[x*2].sum+tree[x*2+1].sum;  }  void update(int x,int p,int num){      int l=tree[x].l;      int r=tree[x].r;      int mid=(l+r)/2;      if(l==r){          tree[x].sum+=num;          return;      }      if(p<=mid)          update(x*2,p,num);      else          update(x*2+1,p,num);      tree[x].sum=tree[x*2].sum+tree[x*2+1].sum;  }  void query(int x,int l,int r){      if(tree[x].l==l&&tree[x].r==r){          ans+=tree[x].sum;          return;      }      int mid=(tree[x].l+tree[x].r)/2;      if(r<=mid)          query(x*2,l,r);      else if(l>mid)          query(x*2+1,l,r);      else{          query(x*2,l,mid);          query(x*2+1,mid+1,r);      }  }  int main(){      int t,x,y,k=1;      char str[10];      scanf("%d",&t);      while(t--){          printf("Case %d:\n",k);k++;          scanf("%d",&n);          for(int i=1;i<=n;i++)              scanf("%d",&a[i]);          create(1,1,n);          while(scanf("%s",str)){              if(str[0]=='E')break;              if(str[0]=='A'){                  scanf("%d%d",&x,&y);                  update(1,x,y);              }              if(str[0]=='S'){                  scanf("%d%d",&x,&y);                  update(1,x,-y);              }              if(str[0]=='Q'){                  ans=0;                  scanf("%d%d",&x,&y);                  query(1,x,y);                  printf("%d\n",ans);              }          }      }      return 0;  }