ZOJ Yukari's Birthday

题意
1+k+k^2+...+k^r=n
或者
k+k^2+...+k^r=n;
给定n
求满足上面其中一个的r和k
输出r*k最小

有相同的r*k值 输出r较小的

使用二分查找

#include<cstdio>
#include<cmath>
typedef long long ll;
ll k,r;

ll myp(ll p,ll pn)
{
	ll ret=1;
	while(pn>0)
	{
		pn--;
		ret*=p;
	}
	return ret;
}

ll sum(ll tk,ll tr)
{
	if(tk==1)
	{
		return tk;
	}
	return ( (myp(tk,tr+1)-1) /(tk-1) );
}

void fun(ll tr,ll n)   //二分查找
{
	ll min=1;
	ll max=(ll)pow((double)n,(double)1/(double)tr) + 1;
	ll mid;
	while(min<max)
	{
		mid=(min+max)/2;
		if(sum(mid,tr)<n)
		{
			min=mid+1;
		}
		else
		{
			max=mid;
		}
	}
	if(sum(min,tr) == n)
	{
		if(tr*min<r*k)
		{
			r=tr;
			k=min;
		}
		else if(tr*min == r*k && tr < r)
		{
			r=tr;
			k=min;
		}
	}
}

void cal(ll n)
{
	ll i;
	ll t=(ll)( log( (double) ( n+1 ) ) / log( (double) 2) );
	for(i=2;i<=t;i++)
	{
		fun(i,n);
	}
}

int main()
{
	ll n;
	while(~scanf("%lld",&n))
	{
		r=1;
		k=n-1;
		cal(n);
		cal(n+1);
		printf("%lld %lld\n",r,k);
	}
}