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[4]={1,-1,0,0};
const int dy[4]={0,0,1,-1};
const int day[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
const int N6=1000006;
const int N5=100006;
const int N4=10006;
const int N3=1006;
const int N2=106;
const int N=210009;
const int MOD=1000000007;
const LL LMAX=0x7fffffffffffffff;
const LL IMAX=0x3fffffff;
const double PI=3.14159265359;
//--------------------------------------------------------
template< class T > T gcd(T a, T b) { return (b != 0 ? 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 << 2];
Node node
;
int  a
, last[1000009];
LL ans
;
int cmp(Node i, Node j)
{
return i.r < j.r ;
}
void PushUP(int rt)
{
tree[rt].sum = tree[rt << 1].sum + tree[rt << 1 | 1].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) >> 1;
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) >> 1;
LL res = 0;
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 = 0;
return;
}
int m = (l + r) >> 1;
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 + 1, node + 1 + m, cmp);
build(1, n, 1);
int np = 1;
mem(last, 0);
foru(i, n){
if(last[a[i]])update(last[a[i]], -a[i], 1, n, 1);
update(i, a[i], 1, n, 1);
while(node[np].r == i && np <= m){
ans[node[np].id] = query(node[np].l, node[np].r, 1, n, 1);
np++;
}
last[a[i]] = i;
}
foru(i, m)pfL(ans[i]),newLine;
}
return 0;
}

View Code