HDU 3874 Necklace 区间查询的离线操作

题目： http://acm.hdu.edu.cn/showproblem.php?pid=3874

对需要查询的区间按右端点排序，然后从左到右依次加入序列中的元素，同时更新，更新的方法是，把上一次出现a[i]值的点变为0，这一次a[i]值的点（即 i）变为a[i],这样保证了前i个元素中只存在一个等于a[i]值得元素，那为什么这样不会影响后面的查询呢？

因为是处理到i点，则把右边界等于a[i]的查询处理掉，剩下的待查询的区间右边界在i点之后，如果左边界在i之前，那么也会包含i点，也就包含了i点的值，由于i以前没有等于a[i]的点，所以只包含了一个这样的值，如果左边界在i之后，前面的操作对它就没影响了。也可以这样理解，当前处理到i点，如果后面的待查询区间的左边界要包含上一个值为a[i]的点，那么它必须也包含了i点，所以i之前等于a[i]的点完全可以舍弃-----------------原来先排序的处理方式还有个专业名字叫=======离线操作

话不多说，看代码：

 /**********************************************
 ***    Problem:
 ***    Author:        JKL
 ***    University:    CSUST
 ***    Team:          __Dream
 ***    Email:          1451108308@QQ.COM
 ***    My Blog:        http://www.cnblogs.com/jklongint/
 ***********************************************/
 //===================================================
 #include <iostream>
 #include <fstream>
 #include <sstream>
 #include <iomanip>
 #include <cstdio>
 #include <cstdlib>
 #include <cmath>
 #include <cassert>
 #include <numeric>
 #include <ctime>
 #include <algorithm>
 #include <cstring>
 #include <string>
 #include <vector>
 #include <queue>
 #include <map>
 #include <stack>
 #include <list>
 #include <set>
 #include <bitset>
 #include <deque>
 using namespace std;
 //---------------------------------------------------
 #define mem(a,b) memset(a,b,sizeof(a))
 #define GO cout<<"HelloWorld!"<<endl
 #define Case(x) cout<<"Case "<<x<<":"
 #define foru(i,n) for(int i=1; i <= n; i++)
 #define ford(i,n) for(int i = n; i >= 1; i--)
  #define fin freopen("input.txt","r",stdin);
  #define fout freopen("output.txt","w",stdout)
 #define lson  l, m, rt << 1
 #define rson  m + 1, r, rt << 1 | 1

 #define sqr(a)  ((a)*(a))
 #define abs(a) ((a>0)?(a):-(a))
 #define pii pair<int,int>

 #define fmax(a,b) max(a,b)
 #define fmin(a,b) min(a,b)
 #define fmax3(a,b,c)  (fmax(a,fmax(a,b)))
 #define fmin3(a,b,c)  (fmin(a,fmin(a,b)))

 #define sfi(x) scanf("%d",&x)
 #define sfL(x) scanf("%I64d",&x)
 #define sfc(x) scanf("%c",&x)
 #define sfd(x) scanf("%lf",&x)
 #define sfs(x) scanf("%s",x)
 #define sfii(a,b) scanf("%d%d",&a,&b)
 #define sfLL(a,b) scanf("%I64d%I64d",&a,&b)
 #define sfcc(a,b) scanf("%c%c",&a,&b)
 #define sfdd(a,b) scanf("%lf%lf",&a,&b)
 #define sfss(a,b) scanf("%s%s",a,b)

 #define pfi(x) printf("%d",x)
 #define pfL(x) printf("%I64d",x)
 #define pfs(x) printf("%s",x)
 #define pfd(x) printf("%lf",x)
 #define pfc(x) print("%c",x)
 #define newLine pfs("\n")
 #define space pfs(" ")

 //--------------------------------------------------------
 typedef __int64 LL;
 typedef unsigned long long ULL;
 //typedef __int64 __LL;
 typedef unsigned __int64 __ULL;

 typedef vector<int> vi;
 typedef vector<LL> vL;
 typedef vector<string> vs;
 typedef set<int> si;
 typedef map<int,int> mii;
 typedef map<LL,LL> mLL;
 typedef map<string,int> msi;
 typedef map<char,int> mci;
 //--------------------------------------------------------
 const int dx[]={,-,,};
 const int dy[]={,,,-};
  const int day[]={,,,,,,,,,,,,};
  const int N6=;
  const int N5=;
  const int N4=;
  const int N3=;
  const int N2=;
  const int N=;
  const int MOD=;
  const LL LMAX=0x7fffffffffffffff;
  const LL IMAX=0x3fffffff;
  const double PI=3.14159265359;
 //--------------------------------------------------------
 template< class T > T gcd(T a, T b) { return (b !=  ? gcd<T>(b, a%b) : a); }
 template< class T > T lcm(T a, T b) { return (a / gcd<T>(a, b) * b); }

 //------------------------------------------------------------
 struct TreeNode{
     LL  sum;
 };
 struct Node{
     int l, r, id;
 };
 //=================================================================
 TreeNode tree[N << ];
 Node node[N];
 int  a[N], last[];
 LL ans[N];
 int cmp(Node i, Node j)
 {
     return i.r < j.r ;
 }
 void PushUP(int rt)
 {
     tree[rt].sum = tree[rt << ].sum + tree[rt <<  | ].sum;
 }
 void update(int p, int x, int l , int r, int rt)
 {
     if(l == r){
         tree[rt].sum += x;
         return;
     }
     int m = (l + r) >> ;
     if(p <= m)update(p, x, lson);
     else update(p, x, rson);
     PushUP(rt);
 }
 LL query(int L, int R, int l, int r, int rt)
 {
     if(L <= l && R >= r){
         return tree[rt].sum;
     }
     int m = (l + r) >> ;
     LL res = ;
     if(L <= m) res += query(L, R, lson);
     if(R > m) res += query(L, R, rson);
     return res;
 }
 void build(int l, int r, int rt)
 {
     if(l == r){
         tree[rt].sum = ;
         return;
     }
     int m = (l + r) >> ;
     build(lson);
     build(rson);
     PushUP(rt);
 }
 int main()
 {
     //fin;//fout;//freopen("input.txt","r",stdin);
     int n, m, T;
     cin >> T;
     while(T--){
         cin >> n ;
         foru(i, n)sfi(a[i]);
         cin >> m;
         foru(i, m)sfii(node[i].l, node[i].r),node[i].id = i;
         sort(node + , node +  + m, cmp);
         build(, n, );
         int np = ;
         mem(last, );
         foru(i, n){
             if(last[a[i]])update(last[a[i]], -a[i], , n, );
             update(i, a[i], , n, );
             while(node[np].r == i && np <= m){
                 ans[node[np].id] = query(node[np].l, node[np].r, , n, );
                 np++;
             }
             last[a[i]] = i;
         }
         foru(i, m)pfL(ans[i]),newLine;
     }
     return ;
 }