luogu3759 [TJOI2017]不勤劳的图书管理员

分块+权值逆序对

#include <algorithm>
#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;
typedef long long ll;
int n, m, uu, vv, blc, bel[50005], ans, ccnt[50005], cval[500005], num[255];
int sum[255][255];
const int mod=1e9+7;
struct Node{
	int idx, val;
}nd[50005], qwq[255][255];
bool cmp1(Node x, Node y){
	return x.idx<y.idx;
}
int lb(int x){
	return x&-x;
}
void bitAdd(int x, int y){
	for(int i=x; i<=n; i+=lb(i)){
		ccnt[i]++;
		cval[i] = (cval[i] + y) % mod;
	}
}
int bitQuery(int x, int &qaq){
	int re=0;
	for(int i=x; i; i-=lb(i)){
		qaq += ccnt[i];
		re = (re + cval[i]) % mod;
	}
	return re;
}
int query1(int l, int r, Node x){
	if(l>r)	return 0;
	int re=0;
	if(bel[l]==bel[r]){
		for(int i=l; i<=r; i++)
			if(nd[i].idx>x.idx)
				re = (re + (nd[i].val+x.val)%mod) % mod;
	}
	else{
		for(int i=bel[l]+1; i<=bel[r]-1; i++){
			int pos=lower_bound(qwq[i]+1, qwq[i]+1+num[i], x, cmp1)-qwq[i];
			int cnt=num[i]-pos+1;
			re = (re + (ll)cnt * x.val) % mod;
			re = (re + ((sum[i][num[i]] - sum[i][pos-1])%mod + mod)%mod) % mod;
		}
		for(int i=l; i<=bel[l]*blc; i++)
			if(nd[i].idx>x.idx)
				re = (re + (nd[i].val+x.val)%mod) % mod;
		for(int i=(bel[r]-1)*blc+1; i<=r; i++)
			if(nd[i].idx>x.idx)
				re = (re + (nd[i].val+x.val)%mod) % mod;
	}
	return re;
}
int query2(int l, int r, Node x){
	if(l>r)	return 0;
	int re=0;
	if(bel[l]==bel[r]){
		for(int i=l; i<=r; i++)
			if(nd[i].idx<x.idx)
				re = (re + (nd[i].val+x.val)%mod) % mod;
	}
	else{
		for(int i=bel[l]+1; i<=bel[r]-1; i++){
			int pos=lower_bound(qwq[i]+1, qwq[i]+1+num[i], x, cmp1)-qwq[i];
			int cnt=pos-1;
			re = (re + (ll)cnt * x.val) % mod;
			if(cnt)	re = (re + sum[i][cnt]) % mod;
		}
		for(int i=l; i<=bel[l]*blc; i++)
			if(nd[i].idx<x.idx)
				re = (re + (nd[i].val+x.val)%mod) % mod;
		for(int i=(bel[r]-1)*blc+1; i<=r; i++)
			if(nd[i].idx<x.idx)
				re = (re + (nd[i].val+x.val)%mod) % mod;
	}
	return re;
}
void gouzao(int x){
	num[x] = 0;
	for(int i=(x-1)*blc+1; i<=min(x*blc, n); i++)
		qwq[x][++num[x]] = nd[i];
	sort(qwq[x]+1, qwq[x]+1+num[x], cmp1);
	for(int i=1; i<=num[x]; i++){
		sum[x][i] = qwq[x][i].val;
		sum[x][i] = (sum[x][i] + sum[x][i-1]) % mod;
	}
}
int main(){
	cin>>n>>m;
	blc = sqrt(n);
	for(int i=1; i<=n; i++){
		scanf("%d %d", &nd[i].idx, &nd[i].val);
		bel[i] = (i - 1) / blc + 1;
	}
	for(int i=1; i<=n; i++)
		qwq[bel[i]][++num[bel[i]]] = nd[i];
	for(int i=1; i<=bel[n]; i++)
		gouzao(i);
	for(int i=1; i<=n; i++){
		int tmp1=0, tmp2=0;
		ans = (ans + bitQuery(n, tmp1) - bitQuery(nd[i].idx, tmp2)) % mod;
		ans = (ans + (ll)(tmp1-tmp2)*nd[i].val) % mod;
		bitAdd(nd[i].idx, nd[i].val);
	}
	while(m--){
		scanf("%d %d", &uu, &vv);
		if(uu>vv)	swap(uu, vv);
		ans = (ans - query1(uu+1, vv-1, nd[vv]) + mod) % mod;
		ans = (ans - query2(uu+1, vv-1, nd[uu]) + mod) % mod;
		if(nd[uu].idx>nd[vv].idx)	ans = (ans - (nd[uu].val+nd[vv].val)%mod + mod) % mod;
		swap(nd[uu], nd[vv]);
		gouzao(bel[uu]); gouzao(bel[vv]);
		ans = (ans + query1(uu+1, vv-1, nd[vv])) % mod;
		ans = (ans + query2(uu+1, vv-1, nd[uu])) % mod;
		if(nd[uu].idx>nd[vv].idx)	ans = (ans + (nd[uu].val+nd[vv].val)%mod) % mod;
		printf("%d
", ans);
	}
	return 0;
}