java 使用 int、double 和 long 计算幂
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Using int, double and long in calculation of powers
提问by SweetMello7
I'm having trouble figuring out when to use int, double and long.
我无法弄清楚何时使用 int、double 和 long。
I'm working on calculating the power of an integer and return the result as long as the power provided is not a negative number.
我正在计算整数的幂并返回结果，只要提供的幂不是负数。
For the assignment, I'm required to use the following code to start:
对于作业，我需要使用以下代码开始：
public static long powerN(int number, int power) {
Here's what I came up with:
这是我想出的：
public class PowerCalculator
{
/**
* Calculate the non-negative power of an integer number. If a negative power is input, the method returns 1.
*
* @param number The number to take power.
* @param power The power factor to be taken to.
* @return The calculation result after taking power of the integer number.
*/
public static long powerN(int number, int power) {
if (power > 0)
{
double result = (Math.pow(number, power));
return result;
}
else
{
return 1;
}
}
}
I know I'm messing up the use of int, double or long but I don't know how to fix it.
我知道我搞砸了 int、double 或 long 的使用，但我不知道如何解决。
采纳答案by nramirez
You could do it by yourself:
你可以自己做：
public static long powerN(
int number,
int power
) {
if(power == 0) return 1;
int result = number;
while(power > 1) {
result*=number;
power--;
}
return (long)result;
}
PS: This does not handle negative powers.
PS：这不处理负面权力。
回答by Julian B.
Wait! If you're doing it yourself, use a faster algorithm like Exponentiation by squaring, something like this:
等待！如果您自己做，请使用更快的算法，例如通过平方取幂，如下所示：
long powerN(long number, int power){
long res = 1;
long sq = number;
while(power > 0){
if(power % 2 == 1){
res *= sq;
}
sq = sq * sq;
power /= 2;
}
return res;
}
回答by Gabriel Cypriano
In case you'd like to use Math.pow:
如果您想使用Math.pow：
public static long powerN(int number, int power) {
return (long) Math.pow(number, power);
}
回答by Guest
Option 1: Cast result of Math.pow to long:
选项 1：将 Math.pow 的结果转换为 long：
public class PowerCalculator{
/**
* Calculate the non-negative power of an integer number. If a negative power is input, the method returns 1.
*
* @param number The number to take power.
* @param power The power factor to be taken to.
* @return The calculation result after taking power of the integer number.
*/
public static long powerN(int number, int power) {
// write your code after this line
if (power < 0){
return 1;
} else{
return (long) Math.pow(number, power);
}
Option 2: without using Math.pow
选项 2：不使用 Math.pow
public class PowerCalculator{
/**
* Calculate the non-negative power of an integer number. If a negative power is input, the method returns 1.
*
* @param number The number to take power.
* @param power The power factor to be taken to.
* @return The calculation result after taking power of the integer number.
*/
public static long powerN(int number, int power) {
// write your code after this line
long result = 1;
while (power > 0) {
result *= number;
power--;
}
return result;
}
