[二分] PKU 1840 Eqs

二分：3+2；

# include <stdio.h>
# include <stdlib.h>

# define trq(x) ((x)*(x)*(x))

int a[5];
long long ans = 0;
int h[105];
int f[305*105*105], g[305*105];

/************************************************************/
int cmp(const void *x, const void *y)
{
    return *(int*)x - *(int*)y;
}

int bins(int *v, int key, int n)
{
    int low = 0, high = n-1, mid, x, y;
    if (key<v[0] || key>v[high])
        return 0;
    while (low+1 < high)
    {
        mid = low + ((high-low)>>1);
        if (v[mid] >= key) high = mid;
        else low = mid;
    }
    x = (v[low]==key ? low-1:low);
    low = 0, high = n-1;
    while (low+1 < high)
    {
        mid = low + ((high-low)>>1);
        if (v[mid] <= key) low = mid;
        else high = mid;
    }
    y = (v[high]==key ? high:high-1);
    return y-x;
}

/************************************************************/

int main()
{
    int i, j, k, n = 0, m = 0;
    
    for (i = 0; i < 5; ++i) scanf("%d", &a[i]);
    for (i = -50; i <= 50; ++i) if (i != 0)
    for (j = -50; j <= 50; ++j)    if (j != 0)
    {
        g[n++] = trq(i)*a[3]+trq(j)*a[4];
        for (k = -50; k <= 50; ++k) if (k != 0)
            f[m++] = trq(i)*a[0]+trq(j)*a[1]+trq(k)*a[2];
    }
    qsort(g, n, sizeof(g[0]), cmp);
    qsort(f, m, sizeof(f[0]), cmp);
    
    for (i = 0; i < n; ++i)
        ans += bins(f, -g[i], m);
    printf("%lld\n", ans);

    return 0;
}