1. 程式人生 > >HDU 5726 GCD(RMQ+二分)(線段樹也可)

HDU 5726 GCD(RMQ+二分)(線段樹也可)

Problem Description

Give you a sequence of N(N≤100,000) integers : a1,...,an(0<ai≤1000,000,000). There are Q(Q≤100,000) queries. For each query l,r you have to calculate gcd(al,,al+1,...,ar) and count the number of pairs(l′,r′)(1≤l<r≤N)such that gcd(al′,al′+1,...,ar′) equal gcd(al,al+1,...,ar).

Input

The first line of input contains a number T, which stands for the number of test cases you need to solve.

The first line of each case contains a number N, denoting the number of integers.

The second line contains N integers, a1,...,an(0<ai≤1000,000,000).

The third line contains a number Q, denoting the number of queries.

For the next Q lines, i-th line contains two number , stand for the li,ri, stand for the i-th queries.

Output

For each case, you need to output “Case #:t” at the beginning.(with quotes, t means the number of the test case, begin from 1).

For each query, you need to output the two numbers in a line. The first number stands for gcd(al,al+1,...,ar) and the second number stands for the number of pairs(l′,r′) such that gcd(al′,al′+1,...,ar′) equal gcd(al,al+1,...,ar).

Sample Input

1
5
1 2 4 6 7
4
1 5
2 4
3 4
4 4

Sample Output

Case #1:
1 8
2 4
2 4
6 1

可蛋疼的一個題,一開始想用線段樹來搞,但是第二部分的查詢沒想出來,發現網上大神們多用RMQ解決,學習一番後總結如下:

這題能用rmq是因為滿足rmq那個轉移方程(還是線段樹更全能啊。。。);

區間增長後gcd快速減小至1也是降低時間複雜度的重要依據;

第二部分直接對每個L,進行對R的二分,用map統計得出結果;

程式碼如下:

#include <bits/stdc++.h>
#define rep(i,j,k) for(int i = j; i <= k; i++) #define LL long long using namespace std; int n, m; int f[100010][18]; int a[100010]; map<int, LL>mp; int gcd(int a, int b) {return b?gcd(b,a%b):a;} void rmq(){ rep(i,1,n) f[i][0] = a[i]; rep(j,1,17) rep(i,1,n) if(i+(1<<j)-1 <= n) f[i][j] = gcd(f[i][j-1], f[i+(1<<j-1)][j-1]); } int ser(int l, int r){ int k = (int)log2((double)(r - l + 1)); return gcd(f[l][k],f[r-(1<<k)+1][k]); } void setTable(){ mp.clear(); rep(i,1,n){ int g = f[i][0],j = i; while(j <= n){ int l = j, r = n; while(l < r){ int mid = (l+r+1)>>1; if(ser(i, mid) == g) l = mid; else r = mid - 1; } mp[g] += l-j+1; j = l + 1; g = ser(i,j); } } } int main(){ int t, l, r; int cas = 1; cin >> t; while(t--){ cin >> n; rep(i,1,n) scanf("%d", a+i); rmq(); setTable(); cin >> m; printf("Case #%d:\n", cas++); rep(i,0,(m-1)){ scanf("%d%d", &l, &r); int tmp = ser(l, r); printf("%d %I64d\n", tmp, mp[tmp]); } } return 0; }

學習到新東西了…