HDU 4282 A very hard mathematic problem(二分查找）

题目链接

网络赛啊。。。知道了算法还错了N次，托了N天，开始的代码+上一句话就AC了，TLE，我以为二分写搓了呢。。。

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <cstdlib>
#define ll __int64
ll f(int x,int z)
{
    int i;
    ll ans = 1;
    for(i = 1;i <= z;i ++)
    {
        ans *= x;
        if(ans > 2147483647)//这里会越界，而且加上这句话效率也会大大提高。
        return 2147483647;
    }
    return ans;
}
int main()
{
    int x,z,n,k,num,str,end,mid;
    ll sv,ss;
    while(scanf("%d",&k)!=EOF)
    {
        if(k == 0) break;
        n = (int)sqrt(k+0.5);
        num = 0;
        for(x = 1;x <= n;x ++)
        {
            for(z = 2;z <= 30;z ++)
            {
                ss = f(x,z);
                sv = x*z;
                if(ss + sv> k)
                break;
                str = x+1;
                end = n;
                while(str < end)
                {
                    mid = (end-str)/2+str;
                    if(ss+f(mid,z)+sv*mid < k)
                    {
                        str = mid+1;
                    }
                    else
                    {
                        end = mid;
                    }
                }
                if(ss+f(str,z)+sv*str == k)
                {
                    num ++;
                }
            }
        }
        printf("%d\n",num);
    }
    return 0;
}