Java实现 洛谷 P1009 阶乘之和

import java.util.Scanner;

public class 阶乘之和 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int [] sum = new int [101];
		int [] num = new int [101];
		num[1]=1;
		for (int i = 1; i <=n; i++) {
			int a=0,b,c;
			for (int j = 1; j < 101; j++) {
				num[j]=num[j]*i+a;
				a=num[j]/10;
				num[j]=num[j]%10;
			}
			a=0;
			for (int j = 0; j < 101; j++) {
				sum[j]=sum[j]+num[j]+a;
				a=sum[j]/10;
				sum[j]%=10;
			}
		}
		boolean a = true;
		for (int i = num.length-1; i >0; i--) {
			if(a&&sum[i]==0){
				continue;
			}
			else {
				a=false;
			}
			System.out.print(sum[i]);
		}
	}

}

PS：

这里有个大佬把样例给破了，小编实属佩服，附下：

if(n==0)cout<<"1"<<endl;//前面的纯手算就可以
if(n==1)cout<<"1"<<endl;
if(n==2)cout<<"3"<<endl;
if(n==4)cout<<"33"<<endl;
if(n==5)cout<<"153"<<endl;
if(n==6)cout<<"873"<<endl;
if(n==7)cout<<"5913"<<endl;
if(n==8)cout<<"46233"<<endl;
if(n==9)cout<<"409113"<<endl;
if(n==10)cout<<"4037913"<<endl;
if(n==11)cout<<"43954713"<<endl;
if(n==12)cout<<"522956313"<<endl;
if(n==13)cout<<"6749977113"<<endl;
if(n==14)cout<<"93928268313"<<endl;
if(n==15)cout<<"1401602636313"<<endl;
if(n==16)cout<<"22324392524313"<<endl;
if(n==17)cout<<"378011820620313"<<endl;
if(n==18)cout<<"6780385526348313"<<endl;
if(n==19)cout<<"128425485935180313"<<endl;//从这里开始最后四位都是0313
if(n==20)cout<<"2561327494111820313"<<endl;
if(n==21)cout<<"53652269665821260313"<<endl;
if(n==22)cout<<"1177652997443428940313"<<endl;
if(n==23)cout<<"27029669736328405580313"<<endl;
if(n==24)cout<<"647478071469567844940313"<<endl;
if(n==25)cout<<"161586881sa373618851684940313"<<endl;
if(n==29)cout<<"9157958657951075573395300940313"<<endl;
if(n==30)cout<<"274410818470142134209703780940313"<<endl;
if(n==31)cout<<"8497 249472648064951935266660940313"<<endl;
if(n==32)cout<<"271628086406341595119153278820940313"<<endl;
if(n==33)cout<<"89 4945705218228090637347680100940313"<<endl;
if(n==34)cout<<"304 187744744822368938255957323620940313"<<endl;
if(n==35)cout<<"10637335711130967298604907294846820940313"<<endl;
if(n==36)cout<<"382630662501032184766604355445682020940313"<<endl;
if(n==37)cout<<"14146383753727377231082583937026584420940313"<<endl;
if(n==38)cout<<"537169001220328488991089808037100875620940313"<<endl;
if(n==39)cout<<"20935051082417771847631371547939998232420940313"<<endl;
if(n==40)cout<<"836850334330315506193242641144055892504420940313"<<endl;
if(n==41)cout<<"34289376947494122614363304694584807557656420940313"<<endl;
if(n==42)cout<<"1439295494700374021157505910939096377494040420940313"<<endl;
if(n==43)cout<<"0313"<<endl;//这里没有样例点
if(n==44)cout<<"0313"<<endl;
if(n==45)cout<<"0313"<<endl;
if(n==46)cout<<"0313"<<endl;
if(n==47)cout<<"0313"<<endl;
if(n==48)cout<<"12678163798554051767172643373255731925167694226950680420940313"<<endl;//最坑的是这里有一个样例点，算杀我也
if(n==49)cout<<"0313"<<endl;
if(n==50)cout<<"0313"<<endl;