203C Photographer

第一道A的纠结；

简单题，WA了几次，最后发现AC的代码 sort 的 cmp 返回的是 bool 型，注意到这点，就 A 了，数据是不会超范围的；

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

# define N 100005

using namespace std;

int n, d, a, b;
int c[N], p[N];
char f[N];

bool cmp(const int &x, const int &y)
{
    return c[x] < c[y];
}

void init(void)
{
    int i, x, y;

    memset(f+1, 0, sizeof(f[0])*n);
    for (i = 1; i <= n; ++i)
    {
        scanf("%d%d", &x, &y);
        c[i] = x*a + y*b;
        p[i] = i;
    }
    sort(p+1, p+n+1, cmp);
}

void solve(void)
{
    int rem, i, cnt;

    cnt = 0;
    rem = d;
    for (i = 1; i <= n; ++i)
    {
        if (rem >= c[p[i]])
        {
            ++cnt;
            f[p[i]] = 1;
            rem -= c[p[i]];
        }
        else break;
    }
    printf("%d\n", cnt);
    for (i = 1; i <= n; ++i) if (f[i])
    {
        --cnt;
        printf("%d", i);
        if (cnt == 0) {putchar('\n'); break;}
        else putchar(' ');
    }
}

int main()
{
    while (~scanf("%d%d%d%d", &n, &d, &a, &b))
    {
        init();
        solve();
    }

    return 0;
}

http://codeforces.com/problemset/problem/203/C