习题 92：高精度算阶乘★★

/*题目描述：
算出n!的完整结果，其中n!=1*2*3*...*n

输入：
多组测试数据，一行一组，每行仅一个数n
其中0<=n<=10000

输出：
输出相应的n!的结果，必须精确到个位

样例输入：
10
20
100

样例输出：
3628800
2432902008176640000
933262154439441526816992388562667004907159682643816214685929
638952175999932299156089414639761565182862536979208272237582
51185210916864000000000000000000000000

其它信息：
最后一个100!的结果由于过长，故拆分成三行，每行60字符，请见谅

难度：Easy

*/

#include <iostream>
#include <iomanip>
#define MAX_SIZE 10000
using namespace std;
//end is the last updated bit
int bigMulti(int *result, int n,int size, int end)
{
    int i,j, carry, tmp;
    carry = 0;
    for(j = 1;j <= n; j++)
    {
        for(i = MAX_SIZE; --i >=end;)
        {
            tmp = result[i] * j + carry;
            result[i] = tmp % 10000;
            carry = tmp / 10000;
        }
        while(carry)
        {
            result[--end] = carry % 10000;
            carry /= 10000;
        }
    }
    return end;
}
int main(void)
{
    int n, end;
    int result[MAX_SIZE];//如果这里声明为char会导致速度减慢
    while(EOF!=scanf("%d",&n))
    {
        memset(result,0,MAX_SIZE*sizeof(int));
        result[MAX_SIZE - 1] = 1;// set result to 1
        end = MAX_SIZE - 1;
        end = bigMulti(result, n,MAX_SIZE, end);
        cout << result[end++];
        for(; end < MAX_SIZE;)
        {
            printf("%04d",result[end++]);
        }
        cout << endl;
        //result[j] = 0;
        //cout << result << endl;
    }
    return 0;
}

/*result:

78737

Name: "younthu" Problem ID "92"
Submit Time: 2008/9/28-13:35

G++: Compile OK

Test  1:    Accepted    Time = 0 ms
Test  2:    Accepted    Time = 0 ms
Test  3:    Accepted    Time = 267 ms
--------------------------------
Problem ID     92
Test Result    Accepted
Total Time     267 ms
Total Memory   228 Kb / 2000 Kb
Code Length    817 Bytes
*/

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