Y sequence
Problem Description
Yellowstar likes integers so much that he listed all positive integers in ascending order,but he hates those numbers which can be written as a^b (a, b are positive integers,2<=b<=r),so he removed them all.Yellowstar calls the sequence that formed by the rest integers“Y sequence”.When r=3,The first few items of it are:
2,3,5,6,7,10......
Given positive integers n and r,you should output Y(n)(the n-th number of Y sequence.It is obvious that Y(1)=2 whatever r is).
Input
The first line of the input contains a single number T:the number of test cases.
Then T cases follow, each contains two positive integer n and r described above.
n<=2*10^18,2<=r<=62,T<=30000.
Output
For each case,output Y(n).
Sample Input
2
10 2
10 3
Sample Output
13
14
题意:
给定正整数n和r,定义Y数列为从正整数序列中删除所有能表示成a^b(2 ≤ b ≤ r)的数后的数列,求Y数列的第n个数是多少。
题解:
假设我们知道了cal(x)表示包括x在内的x之前这个序列有多少个数,这个要容斥
我们则二分就好了,但是不要二分,为什么呢,
没有去写二分
总之题解说了二分超时,那么我们不要二分,迭代过去就是了
#include <iostream> #include <cstdio> #include <cmath> #include <cstring> #include <algorithm> #include <vector> using namespace std; const int N = 1e5+20, M = 30005, mod = 1000000007, inf = 0x3f3f3f3f; typedef long long ll; //不同为1,相同为0 //用负数方便计算容斥的符号 const int zz[19] = {-2, -3, -5, -7, -11, -13, -17, -19, -23, -29, -31, -37, -41, -43, -47, -53, -59, -61, -67}; ll n; int r; vector <int> G; void init() { G.clear(); for(int i = 0; abs(zz[i]) <= r; i++) { int temp = G.size(); for(int j = 0; j < temp; j++) { if(abs(zz[i]*G[j]) <= 63) G.push_back(zz[i]*G[j]); } G.push_back(zz[i]); } } ll cal(ll x) { if(x == 1) return 0; ll ans = x; for(int i = 0; i < G.size(); i++) { ll temp = (ll)(pow(x + 0.5, 1.0/abs(G[i]))) - 1; if(G[i] < 0) ans -= temp; else ans += temp; } return ans - 1; } void solve() { init(); ll ans = n; while(1) { ll temp = cal(ans); if(temp == n) break; ans += n - temp; } printf("%I64d\n", ans); } int main() { int T; scanf("%d", &T); while(T--) { scanf("%I64d%d", &n, &r); solve(); } return 0; }
fuck