codeforces Round #184 Div.2 B Continued Fractions

一开始直接用递归求后一个分数式的值，每求一步约分一次，过了小数据，大数据没过……后来发现是因为中间两个long long相乘溢出了……

看了别人的代码才明白，只要思维稍微转化一下，这题就能变得很简单……

#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <algorithm>

using namespace std;

#define LL long long int

const int MAXN = 100;

int n;
LL p, q, a[MAXN];

int main()
{
    //freopen("in.txt", "r", stdin );
    //freopen("out.txt", "w", stdout );
    while ( ~scanf( "%I64d%I64d", &p, &q ) )
    {
        int i;
        scanf( "%d", &n );
        for ( i = 0; i < n; ++i )
            scanf( "%I64d", &a[i] );

        for ( i = 0; i < n; ++i )
        {
            if ( a[i] > p / q || ( i + 1 < n && a[i] * q == p ) ) break;
            p -= q * a[i];
            swap( p, q );
        }

        if ( i == n && !q ) puts("YES");
        else puts("NO");
    }
    return 0;
}