HDU 3199Hamming Problem

Hamming Problem

Time Limit:1000MS     Memory Limit:32768KB     64bit IO Format:%I64d & %I64u

Submit Status Practice HDU 3199

Description

For each three prime numbers p1, p2 and p3, let's define Hamming sequence Hi(p1, p2, p3), i=1, ... as containing in increasing order all the natural numbers whose only prime divisors are p1, p2 or p3. 

For example, H(2, 3, 5) = 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24, 25, 27, ... 

So H5(2, 3, 5)=6. 

 

Input

In the single line of input file there are space-separated integers p1 p2 p3 i.

 

Output

The output file must contain the single integer - Hi(p1, p2, p3). All numbers in input and output are less than 10^18. 

 

Sample Input

7 13 19 100 

 

Sample Output

26590291 

#include <iostream>#include <algorithm>#include <stdio.h>#include <string.h>using namespace std;typedef long long ll;ll num[10000];int main(){ll p1, p2, p3, n;while(~scanf("%I64d%I64d%I64d%i64d", &p1, &p2, &p3, &n)){memset(num, 0, sizeof(num));num[0] = 1;ll t1, t2, t3;ll r1, r2, r3;t1 = t2 = t3 = 0;for(int i = 1; i <= n; ++i){r1 = num[t1] * p1;r2 = num[t2] * p2;r3 = num[t3] * p3;ll minn = min(r1, min(r2, r3));if(minn == r1) ++t1;if(minn == r2) ++t2;if(minn == r3) ++t3;num[i] = minn;}cout << num[n] << endl;}return 0;}

看着给出的数据范围很大，其实 i 的范围在10000 就能过。

刚开始没有思路，看了别人的代码才恍然大悟。