学步园

以纵坐标为编号建树状数组优化动态规划

#include<algorithm>
#include<iostream>
#include<cstdio>
#define mod 100007
using namespace std;
struct point{
	int x,y;
}p[100001];
int n,K,f[100001][16][2],a[16][2][100001],ans;
inline bool cmp(point x,point y){
	return x.x<y.x;
}
inline void add(int x,int v,int j,int k){
	for(int i=x;i<=100000;i+=(i&(-i)))
	    a[j][k][i]=(a[j][k][i]+v)%mod;
}
inline int que(int x,int j,int k){
	int sum=0;
	for(int i=x;i;i-=(i&(-i)))
	    sum=(sum+a[j][k][i])%mod;
	return sum;
}
int main(){
	//freopen("line.in","r",stdin);
	//freopen("line.out","w",stdout);
	scanf("%d%d",&n,&K);
	for(int i=1;i<=n;i++)
		scanf("%d%d",&p[i].x,&p[i].y);
	sort(p+1,p+n+1,cmp);
	for(int i=1;i<=n;i++){
		f[i][0][0]=f[i][0][1]=1;
		add(p[i].y,1,0,0);add(p[i].y,1,0,1);
		for(int j=1;j<=K;j++){
            f[i][j][0]+=que(p[i].y-1,j,0)+que(p[i].y-1,j-1,1);
            f[i][j][1]+=que(100000,j,1)-que(p[i].y,j,1)+que(100000,j-1,0)-que(p[i].y,j-1,0);
            f[i][j][0]%=mod;f[i][j][1]%=mod;
            if(f[i][j][1]<0)f[i][j][1]+=mod;
            add(p[i].y,f[i][j][0],j,0);add(p[i].y,f[i][j][1],j,1);
        }
	}
	for(int i=1;i<=n;i++){
	    ans=(ans+f[i][K][0])%mod;
		ans=(ans+f[i][K][1])%mod;
	}
	printf("%d\n",ans);
	return 0;
}