Leetcode Climbing Stairs logN 做法

class _2by2{private:    int d00,d01,d10,d11;public:    _2by2(int d00,int d01,int d10,int d11):d00(d00),d01(d01),d10(d10),d11(d11){}        void operator *= (const _2by2& rhs){         int td00 = this->d00 * rhs.d00 + this->d01 * rhs.d10;         int td01 = this->d00 * rhs.d01 + this->d01 * rhs.d11;         int td10 = this->d10 * rhs.d00 + this->d11 * rhs.d10;         int td11 = this->d10 * rhs.d01 + this->d11 * rhs.d11;         this->d00 = td00;         this->d10 = td10;         this->d01 = td01;         this->d11 = td11;    }        int get00(){        return d00;    }};class Solution {private:    _2by2 power(_2by2& multiplier, int n){          _2by2 ans(1,0,0,1);           while(n){              if(n & 1){                 ans *= multiplier;              }              multiplier *= multiplier;              n = n >> 1;          }          return ans;    }public:    int climbStairs(int n) {        _2by2 multiplier(1,1,1,0);        return power(multiplier,n).get00();    }};