【HDOJ】1042 N!

肯定是大叔，本来以为用加法做乘法，后来想想这样麻烦，还是可以使用乘法的，按位乘，ov可以看成不止一位，程序如下所示：

#include <stdio.h>

#define MAX 40000

int main() {
    unsigned int res[MAX];
    int n;
    int ov, i, j, k;
    int pos;


    while (scanf("%d", &n) != EOF) {
        res[0] = 1;
        pos = 1;

        for (i=1; i<=n; i++) {
            ov = 0;
            for (j=0; j<pos; j++) {
                k = res[j] * i + ov;
                res[j] = k%10;
                ov = k / 10;
            }

            while (ov) {
                res[pos++] = ov % 10;
                ov /= 10;
            }
        }

        for (i=pos-1; i>=0; i--)
            printf("%d", res[i]);
        printf("\n");
    }

    return 0;
}