裸搜，每次把剩下的蛋糕分為兩部分。

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <cmath>
using namespace std;
double s;
double dfs(double x,double y,int n)
{
    if(n==1)
    {
        return max(x/y,y/x);
    }
    double ans=1e10;
    for(int i=1;i<=n/2;i++)
    {
        double tx=x*i/n,ty=y*i/n;
        ans=min(ans,max(dfs(tx,y,i),dfs(x-tx,y,n-i)));  
        ans=min(ans,max(dfs(x,ty,i),dfs(x,y-ty,n-i)));  
    }
    return ans;
}
int x,y,n;
int main()
{
    scanf("%d%d%d",&x,&y,&n);
    s=(x*y)/n;
    printf("%lf",dfs(x,y,n));
    return 0;
}