[BZOJ2120][BZOJ2453]数颜色

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cctype>
#include <algorithm>
#include <set>
using namespace std;

int read() {
	int x = 0, f = 1; char c = getchar();
	while(!isdigit(c)){ if(c == ‘-‘) f = -1; c = getchar(); }
	while(isdigit(c)){ x = x * 10 + c - ‘0‘; c = getchar(); }
	return x * f;
}

#define maxn 10010
#define maxcol 1000010
#define maxnode 7840010

int ToT, sumv[maxnode], lc[maxnode], rc[maxnode];
void update(int& y, int x, int l, int r, int p, int v) {
	sumv[y = ++ToT] = sumv[x] + v;
	if(l == r) return ;
	int mid = l + r >> 1; lc[y] = lc[x]; rc[y] = rc[x];
	if(p <= mid) update(lc[y], lc[x], l, mid, p, v);
	else update(rc[y], rc[x], mid + 1, r, p, v);
	return ;
}
int query(int o, int l, int r, int qr) {
	if(r <= qr) return sumv[o];
	int mid = l + r >> 1, ans = query(lc[o], l, mid, qr);
	if(qr > mid) ans += query(rc[o], mid + 1, r, qr);
	return ans;
}

int rt[maxn], Rt[maxn];
int n, A[maxn], pre[maxn], lst[maxcol];
void change(int p, int val) {
	for(int x = p; x <= n; x += x & -x)
		update(Rt[x], Rt[x], 0, n, pre[p], -1),
		update(Rt[x], Rt[x], 0, n, val, 1);
	pre[p] = val;
	return ;
}
int Art[maxn], cntA, Drt[maxn], cntD;
void getrt(int A[], int& cnt, int x) {
	cnt = 0;
	for(; x; x -= x & -x) A[++cnt] = Rt[x];
	return ;
}
int ask(int ql, int qr) {
	getrt(Art, cntA, qr); Art[++cntA] = rt[qr];
	getrt(Drt, cntD, ql - 1); Drt[++cntD] = rt[ql-1];
	int sum = 0;
	for(int i = 1; i <= cntA; i++) sum += query(Art[i], 0, n, ql - 1);
	for(int i = 1; i <= cntD; i++) sum -= query(Drt[i], 0, n, ql - 1);
	return sum;
}

set <int> colpos[maxcol];

int main() {
	n = read(); int q = read();
	for(int i = 0; i < maxcol; i++) colpos[i].insert(0);
	for(int i = 1; i <= n; i++) {
		A[i] = read();
		pre[i] = lst[A[i]];
		lst[A[i]] = i;
		colpos[A[i]].insert(i);
	}
	
	for(int i = 1; i <= n; i++) update(rt[i], rt[i-1], 0, n, pre[i], 1);
	char cmd[5];
	while(q--) {
		scanf("%s", cmd);
		if(cmd[0] == ‘Q‘) {
			int l = read(), r = read();
			printf("%d\n", ask(l, r));
		}
		if(cmd[0] == ‘R‘) {
			int p = read(), col = read();
			if(A[p] == col) continue;
			
			// it -> next  ttit -> now  tit -> pre
			set <int> :: iterator it = colpos[A[p]].lower_bound(p), tit = it, ttit;
			it++; tit--;
			if(it != colpos[A[p]].end()) change(*it, *tit);
			colpos[A[p]].erase(p);
			
			colpos[col].insert(p);
			it = colpos[col].lower_bound(p); ttit = tit = it;
			it++; tit--;
			if(it != colpos[col].end()) change(*it, *ttit);
			change(*ttit, *tit);
			
			A[p] = col;
		}
	}
	
	return 0;
}