HDU-6182(A Math Problem)

给定n求满足k^k < n的数的个数, 数据范围 n < 1e18, 应用快速幂.

#include <iostream>

using namespace std;

typedef long long LL;

LL qpow(LL x, LL n)
{
    LL result = 1;
    while(n) {
        if(n & 1)
            result = result*x;
        n >>= 1;
        x = x*x;
    }
    return result;
}

int main()
{
    LL n;

    while(cin >> n) {
        LL i;
        for(i = 1l; i <= 15l; i++)
            if(qpow(i, i) > n)
                break;

        cout << i - 1 << endl;
    }

    return 0;
}