CodeForces 785E Anton and Permutation

#include <cstdio>
#include <cmath>
#include <cstring>
#include <map>
#include <algorithm>
using namespace std;

int n,m;

int b[200010];//每一个位置属于哪一块
int L[200010];//每一块最左端
int R[200010];//每一块最右端

int x[200010];//原数组
int y[200010];//分块后排序的数组

int main()
{
	scanf("%d%d",&n,&m);

	int sz = (int)sqrt(1.0*n);

	for(int i=0;i<=200000;i++)
	{
		L[i] = 200001;
		R[i] = 0;
	}
	
	for(int i=1;i<=n;i++) 
	{
		b[i] = i/sz;
		L[b[i]] = min(L[b[i]],i);
		R[b[i]] = max(R[b[i]],i);
	}

	for(int i=1;i<=n;i++) x[i] = i, y[i] = i;
	
	long long ans = 0;
	
	while(m--)
	{
		int p1,p2; scanf("%d%d",&p1,&p2);
		if(p1>p2) swap(p1,p2);
		
		if(p1==p2)
		{
			printf("%lld\n",ans);
			continue;
		}

		//属于同一块
		if(b[p1]==b[p2])
		{
			for(int i=p1+1;i<=p2-1;i++) 
			{
				if(x[i]<x[p1]) ans--;
				if(x[i]>x[p1]) ans++;

				if(x[i]<x[p2]) ans++;
				if(x[i]>x[p2]) ans--;
			}

			if(x[p1]<x[p2]) ans++;
			else ans--;

			swap(x[p1],x[p2]);
		}

		//属于相邻两块
		else if(b[p1]+1 == b[p2])
		{
			for(int i=p1+1;i<=p2-1;i++) 
			{
				if(x[i]<x[p1]) ans--;
				if(x[i]>x[p1]) ans++;

				if(x[i]<x[p2]) ans++;
				if(x[i]>x[p2]) ans--;
			}

			if(x[p1]<x[p2]) ans++;
			else ans--;

			int t1 = x[p1], t2 = x[p2];
			swap(x[p1],x[p2]);

			int py1,py2;

			for(int i=L[b[p1]];i<=R[b[p1]];i++) if(y[i] == t1) py1 = i;
			for(int i=L[b[p2]];i<=R[b[p2]];i++) if(y[i] == t2) py2 = i;

			swap(y[py1],y[py2]);
			sort(y+L[b[p1]],y+R[b[p1]]+1);
			sort(y+L[b[p2]],y+R[b[p2]]+1);

		}

		else 
		{
			for(int i=p1+1;i<=R[b[p1]];i++)
			{
				if(x[i]<x[p1]) ans--;
				if(x[i]>x[p1]) ans++;

				if(x[i]<x[p2]) ans++;
				if(x[i]>x[p2]) ans--;
			}

			for(int i=b[p1]+1;i<=b[p2]-1;i++)
			{
				int ll = L[i], rr = R[i], pos=-1;
				while(ll<=rr)
				{
					int mid = (ll+rr)/2;
					if(y[mid]>x[p2]) pos = mid, rr = mid-1;
					else ll = mid+1;
				}
				if(pos == -1) 
				{
					ans = ans - 0;
					ans = ans + R[i] - L[i] + 1;
				}
				else 
				{
					ans = ans - (R[i] - pos + 1);
					ans = ans + (pos  - L[i]);
				}

				ll = L[i], rr = R[i], pos=-1;
				while(ll<=rr)
				{
					int mid = (ll+rr)/2;
					if(y[mid]>x[p1]) pos = mid, rr = mid-1;
					else ll = mid+1;
				}
				if(pos == -1) 
				{
					ans = ans + 0;
					ans = ans - (R[i] - L[i] + 1);
				}
				else 
				{
					ans = ans + (R[i] - pos + 1);
					ans = ans - (pos  - L[i]);
				}
			}

			for(int i=L[b[p2]];i<=p2-1;i++)
			{
				if(x[i]<x[p1]) ans--;
				if(x[i]>x[p1]) ans++;

				if(x[i]<x[p2]) ans++;
				if(x[i]>x[p2]) ans--;
			}

			if(x[p1]<x[p2]) ans++;
			else ans--;

			int t1 = x[p1], t2 = x[p2];
			swap(x[p1],x[p2]);

			int py1,py2;

			for(int i=L[b[p1]];i<=R[b[p1]];i++) if(y[i] == t1) py1 = i;
			for(int i=L[b[p2]];i<=R[b[p2]];i++) if(y[i] == t2) py2 = i;

			swap(y[py1],y[py2]);
			sort(y+L[b[p1]],y+R[b[p1]]+1);
			sort(y+L[b[p2]],y+R[b[p2]]+1);
		}

		printf("%lld\n",ans);
	}

	return 0;
}