UVA10780 Again Prime? No Time.
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题意:输入两个数m,n求最大的整数K使得m^k是n!的约数
题解:将m分解,m = p1^a1*p2^a2*p3^a3.... n!也分解,一个一个分解太慢,素数筛可以快一点,二分K就可以了
#include <bits/stdc++.h> #define N 11100 #define ll long long using namespace std; bool isprime[N]; ll prime[N], num, c[N], temp[N], c1[N], k; void doprime(ll n){ ll i,j; num = 0; memset(isprime, true,sizeof(isprime)); isprime[1] = 0; for(i=2;i<=n;i++){ if(isprime[i]){ prime[num++] = i; for(j=i*i;j<=n;j+=i) isprime[j] = false; } } } ll check(ll k){ ll sum = 0; for(ll i=0; i<num; i++) if(c[i]<k*c1[i]) return 0; return 1; } int main(){ ll n = 5,m = 24, T, nn=1; doprime(10100); scanf("%lld", &T); while(T--){ memset(c1, 0 ,sizeof(c1)); memset(c, 0 ,sizeof(c)); scanf("%lld%lld", &m, &n); for(ll i=1;i<=n;i++) temp[i] = i; for(ll i=0;i<num&&prime[i]<=n;i++){ ll fi = prime[i]; for(ll j=fi;j<=n;j+=prime[i]) while(temp[j]%prime[i] == 0) temp[j] /= prime[i],c[i]++; } for(ll i=1;i<=n;i++) if(temp[i] != 1) c[i]++; for(ll i=0;i<num;i++) while(m%prime[i] == 0) c1[i]++,m /= prime[i]; ll l = 0, r = 1e9, ans = 0; while(l<=r){ ll mid = (l+r)>>1; if(check(mid)) ans = mid, l = mid+1; else r = mid-1; } cout<<"Case "<<nn++<<":\n"; if(ans == 0) cout<<"Impossible to divide\n"; else cout<<ans<<"\n"; } return 0; }
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