hdu5288 OO ' s Sequence (mass factor decomposition + dichotomy)

Title: http://acm.hdu.edu.cn/showproblem.php?pid=5288

Test instructions: interval [l,r], if l<=i<=r, for all I, satisfies a[i]%a[j]!=0 (i!=j) I contribute +1 to the answer. Find out the answers to all the intervals and, among them, 1<=l<=r<=n.

Analysis: Find out the contribution of each number to the answer. For each a[i], the position of the left A[i] nearest and can be rounded out a[i] l[i] and the right away from a[i] nearest and can be complete a[i] r[i], then a[i] The contribution to the answer is (r[i]-i) * (I-l[i]). How to find L[i], first the position of each number in the input order exists in the array, the enumeration of a[i] factor, each enumeration a[i] a factor, two points to the left and right of A[i] The nearest position, update position.

Code:

#include <iostream> #include <cstdio> #include <vector> #include <algorithm>using namespace std ; const int MAXN = 1e5+6;const int mod = 1e9+7;vector <int > Fac[10006];vector <int > Pos[10006];int a[maxn],l[ Maxn],r[maxn];void Init () {int i,j;for (i=1;i<10005;i++) {for (j=1;j*j<=i;j++) {if (i%j==0) {fac[i].push_back (j); if (i/j!=j) fac[i].push_back (i/j);}}} int find_l (int f,int p) {int down=0,mid,up=pos[f].size () -1,ret=-1;while (down<=up) {mid= (Up+down) >>1;if (pos[ f][mid]>=p) up=mid-1;else{down=mid+1;if (Ret<pos[f][mid]) ret=pos[f][mid];}} return ret;} int find_r (int f,int p) {int down=0,mid,up=pos[f].size () -1,ret=1e9;while (down<=up) {mid= (Up+down) >>1;if (pos [F] [mid]<=p) Down=mid+1;else{up=mid-1;if (Ret>pos[f][mid]) ret=pos[f][mid];}} return ret;} int main () {Init (); int N,i,j;while (scanf ("%d", &n)!=eof) {for (i=0;i<=10000;i++) pos[i].clear (); for (i=0;i<n ; i++) {scanf ("%d", &a[i]);p os[a[i]].push_back (i); L[i]=-1; R[i]=n;} for (i=0;i<n;i++) {for (J=0;j<fac[a[i]].size (); j + +) {int f=fac[a[i]][j];int l=find_l (f,i); int R=find_r (f,i); L[i]=max (L,l[i]); R[i]=min (R,r[i]);}} Long Long ans=0;for (i=0;i<n;i++) ans= (ans+ (r[i]-i) * (I-l[i])%mod)%mod;printf ("%i64d\n", ans);} return 0;}

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

hdu5288 OO ' s Sequence (mass factor decomposition + dichotomy)