24.7.23(50. Pow(x, n)(Medium))

class Solution {
public:
    double myPow(double x, int n) 
    {
       long nn = n;
       if(n < 0) nn = -1*nn;

       double val = 1;
       while(nn > 0)
       {
           if(nn % 2 == 0)
           {
               x *= x;
               nn /= 2;
           }
           else 
           {
               val = val * x;
               nn -= 1;
           }
       }
       return (n < 0)? 1/val: val;
    }
};
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class Solution {
    double solve(double x,long n)
    {
        if(n == 0) return 1;
        if(n % 2 == 0) return solve(x*x,n/2);
        else return x*solve(x,n-1);
    }
public:
    double myPow(double x, int n) 
    {
       long nn = n;
       if(n < 0) nn = -1*nn;

       double val = solve(x,nn);
       return (n < 0)? 1/val: val;
    }
};