如果您在编译时知道指数(并且它是一个整数)，您可以使用模板展开循环。这可以更有效，但我想在这里演示基本原则:

#include <iostream>

template<unsigned long N>
unsigned long inline exp_unroll(unsigned base) {
    return base * exp_unroll<N-1>(base);
}

我们使用模板特化来终止递归:

template<>
unsigned long inline exp_unroll<1>(unsigned base) {
    return base;
}

指数需要在运行时已知，

int main(int argc, char * argv[]) {
    std::cout << argv[1] <<"**5= " << exp_unroll<5>(atoi(argv[1])) << ;std::endl;
}

power()函数只适用于整数

int power(int base, unsigned int exp){

    if (exp == 0)
        return 1;
    int temp = power(base, exp/2);
    if (exp%2 == 0)
        return temp*temp;
    else
        return base*temp*temp;

}

复杂度= O(exp)

Power()函数为负exp和浮点基数工作。

float power(float base, int exp) {

    if( exp == 0)
       return 1;
    float temp = power(base, exp/2);       
    if (exp%2 == 0)
        return temp*temp;
    else {
        if(exp > 0)
            return base*temp*temp;
        else
            return (temp*temp)/base; //negative exponent computation 
    }

} 

复杂度= O(exp)

如果你想得到一个整数的2的幂，最好使用shift选项:

Pow(2,5)可以替换为1<<5

这样效率更高。

int pow(int const x, unsigned const e) noexcept
{
  return !e ? 1 : 1 == e ? x : (e % 2 ? x : 1) * pow(x * x, e / 2);
  //return !e ? 1 : 1 == e ? x : (((x ^ 1) & -(e % 2)) ^ 1) * pow(x * x, e / 2);
}

是的，它是递归的，但是一个好的优化编译器会优化递归。

更一般的解决方案考虑负指数

private static int pow(int base, int exponent) {

    int result = 1;
    if (exponent == 0)
        return result; // base case;

    if (exponent < 0)
        return 1 / pow(base, -exponent);
    int temp = pow(base, exponent / 2);
    if (exponent % 2 == 0)
        return temp * temp;
    else
        return (base * temp * temp);
}

除了Elias的答案，当使用有符号整数实现时，会导致未定义行为，当使用无符号整数实现时，会导致高输入的不正确值，

下面是平方求幂的修改版本，它也适用于有符号整数类型，并且不会给出错误的值:

#include <stdint.h>

#define SQRT_INT64_MAX (INT64_C(0xB504F333))

int64_t alx_pow_s64 (int64_t base, uint8_t exp)
{
    int_fast64_t    base_;
    int_fast64_t    result;

    base_   = base;

    if (base_ == 1)
        return  1;
    if (!exp)
        return  1;
    if (!base_)
        return  0;

    result  = 1;
    if (exp & 1)
        result *= base_;
    exp >>= 1;
    while (exp) {
        if (base_ > SQRT_INT64_MAX)
            return  0;
        base_ *= base_;
        if (exp & 1)
            result *= base_;
        exp >>= 1;
    }

    return  result;
}

使用该函数的注意事项:

(1 ** N) == 1
(N ** 0) == 1
(0 ** 0) == 1
(0 ** N) == 0

如果将发生任何溢出或换行，则返回0;

I used int64_t, but any width (signed or unsigned) can be used with little modification. However, if you need to use a non-fixed-width integer type, you will need to change SQRT_INT64_MAX by (int)sqrt(INT_MAX) (in the case of using int) or something similar, which should be optimized, but it is uglier, and not a C constant expression. Also casting the result of sqrt() to an int is not very good because of floating point precission in case of a perfect square, but as I don't know of any implementation where INT_MAX -or the maximum of any type- is a perfect square, you can live with that.