【HDOJ】1099 Lottery

题意超难懂，实则一道概率论的题目。求P(n)。
P(n) = n*(1+1/2+1/3+1/4+...+1/n)。
结果如果可以除尽则表示为整数，否则表示为假分数。

#include <cstdio>
#include <cstring>

#define MAXN 25

__int64 buf[MAXN];

__int64 gcd(__int64 a, __int64 b) {
    if (b == 0) return a;
    else    return gcd(b, a%b);
}

int main() {
    int i, j, k, n;
    __int64 fz, fm, tmp, intr;

    buf[1] = 1;
    for (i=2; i<=22; ++i)
        buf[i] = i*buf[i-1]/gcd(i, buf[i-1]);

    while (scanf("%d", &n) != EOF) {
        fz = 0;
        fm = buf[n];
        for (i=1; i<=n; ++i)
            fz += fm/i;
        fz *= n;
        tmp = gcd(fz, fm);
        fz /= tmp;
        fm /= tmp;
        tmp = fz/fm;
        fz -= tmp*fm;
        if (fz == 0) {
            printf("%I64d
", tmp);
            continue;
        }
        n = 0;
        intr = tmp;
        while (tmp) {
            ++n;
            tmp /= 10;
        }
        for (i=0; i<=n; ++i)
            printf(" ");
        printf("%I64d
", fz);
        printf("%I64d ", intr);
        j = k = 0;
        while (fz) {
            ++j;
            fz /= 10;
        }
        tmp = fm;
        while (tmp) {
            ++k;
            tmp /= 10;
        }
        j = (j>k) ? j:k;
        for (i=0; i<j; ++i)
            printf("-");
        printf("
");
        for (i=0; i<=n; ++i)
            printf(" ");
        printf("%I64d
", fm);
    }

    return 0;
}