数值的整数次方

代码

分析

数值的整数次方

代码

public class Solution {
    public double Power(double base, int exponent) {
        if(base==0&&exponent<=0){
            return 0;
        }
        int total=1;
        for(int i=0;i<Math.abs(exponent);i++){
            total*=base;
        }
        if(exponent<0){
            return 1.0/total;
        }
        return total;
    }
    public double Power2(double base, int exponent) {
        if(base==0&&exponent<=0){
            return 0;
        }
        double total=PowerCore(base,Math.abs(exponent));
        if(exponent<0){
            return 1.0/total;
        }
        return total;
    }
    public double PowerCore(double base,int exponent){
        if(exponent==0){
            return 1.0;
        }
        if(exponent==1){
            return base;
        }
        double result=PowerCore(base,exponent>>1);
        result*=result;
        if((exponent&1)==1){//此处一定要加括号，==操作符优先级大于&
            result*=base;
        }
        return result;
    }
}