工厂挑战赛(初学者挑战赛)
工厂挑战赛(初学者挑战赛)
提问于 2012-04-05 02:36:43
我尝试了以下挑战：
给出了前几个阶乘：
1！=1
2！=2 x 1=2
3！=3 x 2 x 1=6
4！=4 x 3 x 2 x 1= 24
前15个阶乘的和是多少，不包括0!？
我的Java解决方案如下：
public class Factorial
{
public static void main(String[] args)
{
int sum = 0;
int multi = 1;
for (int i=1;i<=15;i++)
{
multi = multi*i;
sum = multi+sum;
}
System.out.print(sum);
}
}我验证了前7个工厂的解决方案，但它是否适用于前15个工厂？
回答 3
Stack Overflow用户
回答已采纳
发布于 2012-04-05 02:43:02
不，它在15年内不起作用。使用long。此外，您还可以将print语句移动到循环中，以检查它开始失败的位置。我猜在这种情况下是13。
Stack Overflow用户
发布于 2012-04-05 02:40:50
由于integer overflow的原因，它不适用于前15个阶乘。正确的答案是1401602636313，它超过了Java的int界限2147483647。您可以使用边界为9223372036854775807的long或BigInteger。
Stack Overflow用户
发布于 2012-04-05 02:54:15
那
public static void printFactorials (int max) {
long fac = 1;
long sum = 0;
for (int i = 1; i <= max; fac *= ++i) {
System.out.println(String.format("Factorial(%2d)=%d", i, fac));
sum += fac;
}
System.out.println(String.format("Sum of Factorials(1 to %2d)=%d", max, sum));
}为您提供
Factorial( 1)=1
Factorial( 2)=2
Factorial( 3)=6
Factorial( 4)=24
Factorial( 5)=120
Factorial( 6)=720
Factorial( 7)=5040
Factorial( 8)=40320
Factorial( 9)=362880
Factorial(10)=3628800
Factorial(11)=39916800
Factorial(12)=479001600
Factorial(13)=6227020800
Factorial(14)=87178291200
Factorial(15)=1307674368000
Sum of Factorials(1 to 15)=1401602636313long在21开始失败，下一步是BigInteger
public static void printRlyBigFactorials (int max) {
BigInteger fac = BigInteger.ONE;
BigInteger sum = BigInteger.ZERO;
for (int i = 1; i <= max; ++i) {
fac = fac.multiply(BigInteger.valueOf(i));
sum = sum.add(fac);
System.out.println(String.format("Factorial(%2d)=%d", i, fac));
}
System.out.println(String.format("Sum of Factorials(1 to %2d)=%d", max, sum));
}这将几乎无限期地工作，并可以给你带来奇特的结果，比如：
Sum of Factorials(1 to 500)=
1222581999810786173488382263893486121736784649845260488587055662127413631697
9142090995417259894466676137016242713788312106218384177808117660024733369428
7060019503701220190523381023699528466605036804597249531428694859689049295904
5138704466475196055082304091214424335155644013903958356823605973150159110295
5787828433482529258832635575855564789877227459384652114477297831606218655683
9245588828671235437927278554210732477499719243692398907465554636521289870187
5799458234466791378320221140358905721655475503366304295011345436395868843079
5463780536087239619245051615759218253091986494512882003123090598805090122753
7135918455294416676103707115038417384516670399033063650562275830354903359872
0775172343137459008549361297203752431405977559950082400276439557196120290170
5516606073135650288107937474531851451830365876392678959480905477335825506233
3795849463603798966643420966668878072957663827751761832039623225350606860709
6479320263132522604054741925038640750661849690108363701190203548476572823422
7743271977187818002695582046473911765828511673121820261887951566200568565033
40092247479478684738621107994804323593105039052556442336528920420940313页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/10017267
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