BZOJ 2120: 数颜色

2120

思路1：树状数组套主席树

#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize(4)
#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pi acos(-1.0)
#define LL long long
//#define mp make_pair
#define pb push_back
#define ls rt<<1, l, m
#define rs rt<<1|1, m+1, r
#define ULL unsigned LL
#define pll pair<LL, LL>
#define pii pair<int, int>
#define piii pair<pii, int>
#define mem(a, b) memset(a, b, sizeof(a))
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout);
//head

const int N = 1e4 + 5;
int a[N], root[N], bitroot[N], head[N*2], lson[N*60], rson[N*60], value[N*60], tot = 0, n;
char s[10];
vector<int>vc;
set<int>st[N*2];
set<int>::iterator it, pre, nxt;
pair<int, pii> Q[N];
void build(int &x, int l, int r) {
    x = ++tot;
    if(l == r) {
        value[x] = 0;
        return ;
    }
    int m = l+r >> 1;
    build(lson[x], l, m);
    build(rson[x], m+1, r);
    value[x] = value[lson[x]] + value[rson[x]];
}
void update(int old, int &x, int p, int v, int l, int r) {
    x = ++tot;
    lson[x] = lson[old], rson[x] = rson[old], value[x] = value[old] + v;
    if(l == r) return ;
    int m = l+r >> 1;
    if(p <= m) update(lson[x], lson[x], p, v, l, m);
    else update(rson[x], rson[x], p, v, m+1, r);
}
int query(int x, int l, int r, int k) {
    if(l == r) return value[x];
    int m = l+r >> 1;
    if(k <= m) return query(lson[x], l, m, k);
    else return value[lson[x]] + query(rson[x], m+1, r, k);
}
void add(int x, int p, int v) {
    while(x <= n) {
         update(bitroot[x], bitroot[x], p, v, 0, n);
         x += x&-x;
    }
}
int sum(int x, int k) {
    int ans = query(root[x], 0, n, k);
    while(x) {
        ans += query(bitroot[x], 0, n, k);
        x -= x&-x;
    }
    return ans;
}
void change(int x, int y) {
    int now = a[x];
    pre = it = nxt = st[now].lower_bound(x);
    pre--, nxt++;
    add(x, *pre, -1);
    if(nxt != st[now].end()) add(*nxt, x, -1), add(*nxt, *pre, 1);
    st[now].erase(it);

    a[x] = y;
    st[y].insert(x);
    pre = it = nxt = st[y].lower_bound(x);
    pre--, nxt++;
    add(x, *pre, 1);
    if(nxt != st[y].end()) add(*nxt, x, 1), add(*nxt, *pre, -1);
}
int main() {
    int m;
    scanf("%d %d", &n, &m);
    for (int i = 1; i <= n; i++) scanf("%d", &a[i]), vc.pb(a[i]);
    for (int i = 1; i <= m; i++) {
        scanf("%s", s);
        scanf("%d %d", &Q[i].se.fi, &Q[i].se.se);
        if(s[0] == 'Q') Q[i].fi = 1;
        else Q[i].fi = 2, vc.pb(Q[i].se.se);
    }
    sort(vc.begin(), vc.end());
    vc.erase(unique(vc.begin(), vc.end()), vc.end());
    for (int i = 1; i <= n; i++) a[i] = lower_bound(vc.begin(), vc.end(), a[i]) - vc.begin() + 1;
    for (int i = 1; i <= m; i++) if(Q[i].fi == 2) Q[i].se.se = lower_bound(vc.begin(), vc.end(), Q[i].se.se) - vc.begin() + 1;

    build(root[0], 0, n);
    int sz = (int)vc.size();
    for (int i = 0; i <= sz; i++) st[i].insert(0);
    for (int i = 1; i <= n; i++) {
        update(root[i-1], root[i], head[a[i]], 1, 0, n);
        head[a[i]] = i;
        st[a[i]].insert(i);
    }
    for (int i = 1; i <= n; i++) bitroot[i] = root[0];

    for (int i = 1; i <= m; i++) {
        if(Q[i].fi == 1) {
            printf("%d\n", sum(Q[i].se.se, Q[i].se.fi -1) - sum(Q[i].se.fi - 1, Q[i].se.fi - 1));
        }
        else {
            change(Q[i].se.fi, Q[i].se.se);
        }
    }
    return 0;
}