Sword refers to the integer power of offer acwing 27 (fast power)

Topic

answer

Pit 1. There may be negative numbers in this question. Use fast power to convert it to a positive number, and finally take the reciprocal.
Pit 2. When n is equal to negative infinity, taking the opposite number will exceed the range of int. Long long

Code

class Solution {
    
    
public:
    double Power(double x, int n) {
    
    
    typedef long long LL;
    bool is_minus = n < 0;
    double res = 1;
    LL k = abs(LL(n));
    while (k) {
    
    
        if (k & 1) res = res * x;
        x = x * x;
        k >>= 1;
    }
    if (is_minus) res = 1 / res;
    return res;
}

};