2020 camp-day-e

题解

暴力就行（如果n 3000，那就要优化成 n^2

#include <cstdio>

#define RE register
#define FOR(i,a,b) for(RE int i=a;i<=b;++i)
#define ROF(i,a,b) for(RE int i=a;i>=b;--i)
#define sc(n) scanf("%d",&n)

using namespace std;

int m, n;
int a[305], b[5], e[6];
int tex[301][301];
long long ans;

int main()
{
    sc(n);
    FOR(i, 1, n)
    {
        FOR(j, 1, n)tex[j][i] = tex[j][i - 1];
        sc(a[i]); tex[a[i]][i] += 1;
    }
    FOR(i, 1, 4)
    {
        sc(b[i]);
        FOR(j, 1, i - 1)
            if (b[i] == b[j])
                if (j == 1)e[i - 2] = 1;
                else if (j == 2)e[i] = 1;
                else e[5] = 1;
    }
    FOR(i, 1, n - 3)
        FOR(j, i + 1, n - 2)
        {
            if (e[0] && a[i] != a[j])continue;
            if (!e[0] && a[i] == a[j])continue;
            FOR(x, j + 1, n - 1)
                if ((e[1] && a[i] != a[x]) || (!e[1] && a[i] == a[x]))continue;
                else if ((e[3] && a[j] != a[x]) || (!e[3] && a[j] == a[x]))continue;
                else if (e[2])ans += tex[a[i]][n] - tex[a[i]][x];
                else if (e[4])ans += tex[a[j]][n] - tex[a[j]][x];
                else if (e[5]) ans += tex[a[x]][n] - tex[a[x]][x];
                else ans += n - x - tex[a[i]][n] + tex[a[i]][x] - (!e[0]) * (tex[a[j]][n] - tex[a[j]][x]) - (!e[1] && !e[3]) * (tex[a[x]][n] - tex[a[x]][x]);
        }
    printf("%lld", ans);
    return 0;
}