BZOJ 2038 小Z的袜子(hose) （莫队离线）

#include <iostream>
#include <string.h>
#include <math.h>
#include <queue>
#include <algorithm>
#include <stdlib.h>
#include <map>
#include <set>
#include <stdio.h>
#include <time.h>
using namespace std;
#define LL long long
#define pi acos(-1.0)
#pragma comment(linker, "/STACK:1024000000")
const int mod=1e9+7;
const int INF=0x3f3f3f3f;
const double eqs=1e-9;
const int MAXN=50000+10;
int a[MAXN], ha[MAXN];
LL ans1[MAXN], ans2[MAXN];
struct node
{
int l, r, id, pos;
}fei[MAXN];
LL gcd(LL x, LL y)
{
return y==0?x:gcd(y,x%y);
}
bool cmp(node x, node y)
{
return x.pos<y.pos||(x.pos==y.pos&&x.r<y.r);
}
int main()
{
int n, m, i, j, l, r, k;
LL res, Gcd;
while(scanf("%d%d",&n,&m)!=EOF){
for(i=1;i<=n;i++){
scanf("%d",&a[i]);
}
k=sqrt(n*1.0)+0.5;
for(i=0;i<m;i++){
scanf("%d%d",&fei[i].l,&fei[i].r);
fei[i].id=i;
fei[i].pos=fei[i].l/k;
}
sort(fei,fei+m,cmp);
memset(ha,0,sizeof(ha));
l=1;
r=0;
res=0;
for(i=0;i<m;i++){
while(r>fei[i].r){
res-=(LL)ha[a[r]]-1;
ha[a[r]]--;
r--;
}
while(r<fei[i].r){
r++;
ha[a[r]]++;
res+=(LL)ha[a[r]]-1;
}
while(l>fei[i].l){
l--;
ha[a[l]]++;
res+=(LL)ha[a[l]]-1;
}
while(l<fei[i].l){
res-=(LL)ha[a[l]]-1;
ha[a[l]]--;
l++;
}
ans1[fei[i].id]=res;
ans2[fei[i].id]=(LL)(r-l+1)*(r-l)/2;
}
for(i=0;i<m;i++){
if(!ans1[i]){
puts("0/1");
continue;
}
Gcd=gcd(ans1[i],ans2[i]);
printf("%lld/%lld\n",ans1[i]/Gcd,ans2[i]/Gcd);
}
}
return 0;
}