BZOJ 2038: [2009国家集训队]小Z的袜子(hose) | 莫队

题目:

http://www.lydsy.com/JudgeOnline/problem.php?id=2038

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题解:

开LongLong!!!!

按照莫队的方法把询问拍个序,然后搞cnt数组统计每个颜色出现次数,用cur统计当前方案

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#define N 50010
typedef unsigned long long ll;
using namespace std;
ll n,m,c[N],S,L,R;
ll ans1[N],ans2[N],cnt[N],cur;
struct node
{
    ll l,r,bl,id;
    bool operator < (const node &x)const
    {
        return bl<x.bl || bl==x.bl && r<x.r;
    }
}q[N];
ll gcd(ll x,ll y)
{
    return y?gcd(y,x%y):x;
}
int main()
{
    scanf("%lld%lld",&n,&m);S=sqrt(n),cnt[0]=1;
    for (ll i=1;i<=n;i++)
    scanf("%lld",c+i);
    for (ll i=1,l,r;i<=m;i++)
    {
    scanf("%lld%lld",&q[i].l,&q[i].r);
    q[i].id=i;q[i].bl=(q[i].l-1)/S+1;
    }
    sort(q+1,q+1+m);
    for (ll i=1;i<=m;i++)
    {
    ll tl=q[i].l,tr=q[i].r;
    while (L<tl) cnt[c[L]]--,cur-=cnt[c[L]],L++;
    while (L>tl) L--,cur+=cnt[c[L]],cnt[c[L]]++;
    while (tr>R) R++,cur+=cnt[c[R]],cnt[c[R]]++;
    while (R>tr) cnt[c[R]]--,cur-=cnt[c[R]],R--;
    ans1[q[i].id]=cur;
    ans2[q[i].id]=(tr-tl)*(tr-tl+1LL)/2;
    }
    for (int i=1;i<=m;i++)
    {
    ll G=gcd(ans1[i],ans2[i]);
    printf("%lld/%lld
",ans1[i]/G,ans2[i]/G);
    }
    return 0;
}