SJTU 1123 折线统计 (动态规划&&树状数组)

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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 100007using 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;}

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