HDU3988-Harry Potter and the Hide Story(数论-质因数分解)
2014-07-29 23:25
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Harry Potter and the Hide Story
Time Limit: 10000/5000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)Total Submission(s): 2193 Accepted Submission(s): 530
Problem Description
iSea is tired of writing the story of Harry Potter, so, lucky you, solving the following problem is enough.
Input
The first line contains a single integer T, indicating the number of test cases.
Each test case contains two integers, N and K.
Technical Specification
1. 1 <= T <= 500
2. 1 <= K <= 1 000 000 000 000 00
3. 1 <= N <= 1 000 000 000 000 000 000
Output
For each test case, output the case number first, then the answer, if the answer is bigger than 9 223 372 036 854 775 807, output “inf” (without quote).
Sample Input
2 2 2 10 10
Sample Output
Case 1: 1 Case 2: 2
Author
iSea@WHU
题意:给你n和k,让你求出最大的i 满足n的阶乘能被k的i次方整除。
思路:对k进行质因数分解,求出每个质因数在阶乘中的幂的大小,答案即为最小的那个幂。
#include <iostream> #include <cstdio> #include <cstring> #include <vector> #include <string> #include <algorithm> #include <queue> using namespace std; #define LL unsigned long long const int maxn = 10000005; bool isPrime[maxn]; vector<LL> prime,digit,cnt; void getPrime(){ prime.clear(); memset(isPrime,0,sizeof isPrime); for(LL i = 2; i < maxn; i++){ if(!isPrime[i]){ prime.push_back(i); for(LL j = i*i; j < maxn; j += i) isPrime[j] = 1; } } } void getDigit(LL k){ for(int i = 0; i < prime.size() && k >= prime[i]; i++){ if(k%prime[i]==0){ int tt = 0; digit.push_back(prime[i]); while(k%prime[i]==0){ tt++; k /= prime[i]; } cnt.push_back(tt); } } if(k!=1){ digit.push_back(k); cnt.push_back(1); } } LL getSum(LL n,LL p){ LL res = 0; while(n){ n /= p; res += n; } return res; } int main(){ int ncase,T=1; LL k,n; getPrime(); cin >> ncase; while(ncase--){ cin >> n >> k; if(k==1){ printf("Case %d: inf\n",T++); continue; } LL ans = -1; digit.clear(); cnt.clear(); getDigit(k); for(int i = 0; i < digit.size(); i++){ LL tk = getSum(n,digit[i])/cnt[i]; if(ans == -1) ans = tk; else ans = min(ans,tk); } printf("Case %d: %I64u\n",T++,ans); } return 0; }
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