[HZOI 2015]疯狂的颜色序列

%ad大神的脑洞，这题是强制在线版的HH的项链

所以可以考虑树套树，和主席树之类的做法

对于每个点，可以将这个点的颜色上一次出现的位置插入到主席树里，对于每一个 l ~ r 的询问， l 到 r 之间有多少颜色上一次出现的位置在0 到 l-1 内就是答案

#define MAXN 500010UL
#include <cstdio>
#include <algorithm>

using namespace std;

int n, m, Rt[MAXN], num, ans, lt[MAXN];

struct Seg {
    int ls, rs, val;
}bn[MAXN*20];

void Insert(int lrt, int &rt, int l, int r, int pos) {
    rt = ++ num;
    bn[rt] = bn[lrt];
    if(l==r) {
        ++ bn[rt].val;
        return;
    }
    int mid = (l+r)>>1;
    if(pos<=mid) Insert(bn[lrt].ls, bn[rt].ls, l, mid, pos);
    else Insert(bn[lrt].rs, bn[rt].rs, mid+1, r, pos);
    bn[rt].val = bn[bn[rt].ls].val+bn[bn[rt].rs].val;
    return;
}

void Find(int lrt, int rt, int l, int r, int ls, int rs) {
    if(bn[rt].val-bn[lrt].val<=0) return;
    if(ls<=l&&rs>=r) {
        ans += bn[rt].val-bn[lrt].val;
        return;
    }
    int mid = (l+r)>>1;
    if(ls<=mid) Find(bn[lrt].ls, bn[rt].ls, l, mid, ls, rs);
    if(rs>mid) Find(bn[lrt].rs, bn[rt].rs, mid+1, r, ls, rs);
    return;
}

void In(int &x) {
    x = 0;
    char tmp = getchar();
    while(tmp<'0'||tmp>'9') tmp = getchar();
    while(tmp>='0'&&tmp<='9') x = x*10+tmp-'0', tmp = getchar();
    return;
}

int main() {
    freopen("color_seq.in", "r", stdin);
    freopen("color_seq.out", "w", stdout);
    In(n), In(m);
    for(int i = 1, x ; i <= n ; ++ i) {
        In(x);
        Insert(Rt[i-1], Rt[i], 0, n, lt[x]);
        lt[x] = i;
    }
    for(int i = 1, l, r ; i <= m ; ++ i) {
        In(l), In(r);
        l = (l+ans)%n+1, r = (r+ans)%n+1;
        if(l>r) swap(l, r);
        ans = 0, Find(Rt[l-1], Rt[r], 0, n, 0, l-1);
        printf("%d\n", ans);
    }
    return 0;
}