[英]Java Math issue incorrect output
(51^43)Mod77 in scientific calculator gives 2 as the output however, (51 ^ 43)科学计算器中的Mod77给出2作为输出,
(int)(Math.pow(51,43)%(double)77) gives 12 which should be 2 instead. (int)(Math.pow(51,43)%(double)77)给出的12应该是2。
Can you please help ? 你能帮忙吗?
final BigInteger base = BigInteger.valueOf(51);
final BigInteger exponent = BigInteger.valueOf(43);
final BigInteger modulus = BigInteger.valueOf(77);
System.out.println(base.modPow(exponent, modulus));
prints 2
. 打印
2
。
A double
doesn't have enough precision to hold all the digits of Math.pow(51,43)
. double
精度没有足够的精度来容纳Math.pow(51,43)
所有数字。 So when you take it mod 77
, the answer is prone to significant rounding errors. 因此,当您使用
mod 77
,答案很容易出现明显的舍入错误。
I suggest using BigInteger
for arbitrary precision integer arithmetic. 我建议使用
BigInteger
进行任意精度的整数运算。
Instead of: 代替:
(int)(Math.pow(51,43)%(double)77)
do: 做:
(int)(Math.pow(51,43))%((double)77)
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