51nod 1060 最复杂的数(数论,反素数)
题目链接:https://www.51nod.com/onlineJudge/questionCode.html#!problemId=1060
题解:可以去学习一下反素数。
#include <iostream> #include <cstring> #define inf 1000000000000000007 using namespace std; typedef unsigned long long ull; const int M = 1e6 + 10; ull n , dp[M]; int prime[16] = {2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53}; void dfs(int deep , ull sum , int num) { dp[num] = min(dp[num] , sum); for(int i = 1 ; i <= 63 ; i++) { if(sum > 1e18 / prime[deep]) break; dfs(deep + 1 , sum * prime[deep] , num * (i + 1)); sum *= prime[deep]; } } int main() { int t; scanf("%d" , &t); for(int i = 0 ; i < M ; i++) dp[i] = -inf; dfs(0 , 1 , 1); while(t--) { scanf("%lld" , &n); int ans; for(int i = M - 1 ; i >= 1 ; i--) { if(dp[i] <= n && dp[i] != 0) {ans = i; break;} } printf("%lld %d\n" , dp[ans] , ans); } return 0; }