[cdq分治][树状数组] Jzoj P4419 hole
题解
- 四维偏序问题,cdq分治,再用树状数组记录一个前缀和
代码
1 #include <cstdio> 2 #include <iostream> 3 #include <algorithm> 4 using namespace std; 5 struct edge { int x,y,z,d; }a[900000],b[900000],c1[90000],c2[900000]; 6 int sz[40000000],ans[900000],tot,num,mx,n,x,y,d; 7 bool cmp(edge x,edge y) { return x.z<y.z||(x.z==y.z&&x.d<y.d); } 8 bool cmp1(edge x,edge y) { return x.x<=y.x; } 9 int lowbit(int x) { return x&-x; } 10 void insert(int x,int y) 11 { 12 num=num+y; 13 for (x;x<=mx;x+=lowbit(x)) sz[x]+=y; 14 } 15 int getsum(int x) 16 { 17 int k=num; 18 for (x;x;x-=lowbit(x)) k-=sz[x]; 19 return k; 20 } 21 void work(int l,int r) 22 { 23 if (l==r) return; 24 int mid=(l+r)/2,cnt1=0,cnt2=0; 25 work(l,mid),work(mid+1,r); 26 for (int i=l;i<=mid;i++) if (!b[i].d) c1[++cnt1]=b[i]; 27 for (int i=mid+1;i<=r;i++) if (b[i].d) c2[++cnt2]=b[i]; 28 if (!cnt1||!cnt2) return; 29 sort(c1+1,c1+cnt1+1,cmp1),sort(c2+1,c2+cnt2+1,cmp1); 30 int k=cnt1+1; 31 for (int i=cnt2;i>=1;i--) 32 { 33 while (k>1&&c1[k-1].x>=c2[i].x) insert(c1[--k].y,1); 34 ans[c2[i].d]+=getsum(c2[i].y-1); 35 } 36 for (int i=k;i<=cnt1;i++) insert(c1[i].y,-1); 37 } 38 void cdq(int l,int r) 39 { 40 if (l==r) return; 41 int mid=(l+r)/2; 42 cdq(l,mid),cdq(mid+1,r); 43 int cnt=0,boo=0; 44 for (int i=l;i<=mid;i++) if (!a[i].d) b[++cnt]=a[i]; 45 for (int i=mid+1;i<=r;i++) if (a[i].d) b[++cnt]=a[i],boo=1; 46 if (!boo||!cnt) return; 47 sort(b+1,b+cnt+1,cmp),work(1,cnt); 48 } 49 int main() 50 { 51 scanf("%d",&n); 52 for (int i=1;i<=n;i++) 53 { 54 scanf("%d%d%d",&x,&y,&d); 55 a[i].x=x+1,a[i].y=y+1,a[i].z=x+y+d,mx=max(mx,y+d); 56 if (d!=0) a[i].d=++tot; 57 } 58 cdq(1,n); 59 for (int i=1;i<=tot;i++) printf("%d\n",ans[i]); 60 }