LeetCode 483

LeetCode 483 Smallest Good Base

题目大意

解法：
实在想不出什么办法，就二分吧。。。
代码：https://www.cnblogs.com/grandyang/p/6620351.html

class Solution {
public:
    string smallestGoodBase(string n) {
        long long num = stol(n);
        for(int i=log(num+1)/log(2);i>=2;i--){
            long long left = 2, right = pow(num,1.0/(i-1))+1;
            while(left<right){
                long long mid = left+(right-left)/2,sum = 0;
                for(int j=0;j<i ;j++){
                    sum = sum*mid+1;
                }
                if(sum == num) return to_string(mid);
                if(sum<num) left = mid+1;
                else right = mid;
            }
        }
        return to_string(num-1);
    }
};