題意：

規則：

五張牌均嚴格小於5，五張牌的和小於等於10，得60分。

五張牌都是$J,Q,K$，得50分。

五張牌有四張牌相同，得40分。

如果其中三張牌的和是10的倍數，並且其他兩張牌的和是10的倍數，得30分

如果其中三張牌的和是10的倍數，並且其他兩張牌的和對於10的餘數大於等於7，得$2*$其他兩張牌的和對於10的餘數

如果其中三張牌的和是10的倍數，並且其他兩張牌的和對於10的餘數大於等於7，得其他兩張牌的和對於10的餘數

 其餘情況不得分，同時每次只能獲取最高分。

現在你手上已經有四張牌，求拿到第五張牌後的分數期望（四捨五入）

思路：

預處理出所有情況，最後遍歷一次得到總分後除以13

#include<bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
const ll MOD = 1e9 + 7;
 
int ans[20][20][20][20][20];
 
void Init()
{
    for (int a = 1; a <= 13; ++a)
    {
        for (int b = 1; b <= 13; ++b)
        {
            for (int c = 1; c <= 13; ++c)
            {
                
 
for (int d = 1; d <= 13; ++d)
                {
                    for (int e = 1; e <= 13; ++e)
                    {
                        if (a < 5 && b < 5 && c < 5 && d < 5 && e < 5 && a + b + c + d + e <= 10)
                        {
                            ans[a][b][c][d][e] 
 
= 60;
                        }
                        else if (a >= 11 && b >= 11 && c >= 11 && d >= 11 && e >= 11)
                        {
                            ans[a][b][c][d][e] = 50;
                        }
                        else if ((a == b && b == c && c == d) || (a == b && b == c && c == e) || (a == b && b == d && d == e) || (a == c && c == d && d == e) || (b == c && c == d && d == e))
                        {
                            ans[a][b][c][d][e] = 40;
                        }
                        else
                        {
                            if ((min(10, a) + min(10, b) + min(10, c)) % 10 == 0 || (min(10, a) + min(10, b) + min(10, d)) % 10 == 0 || (min(10, a) + min(10, b) + min(10, e)) % 10 == 0 || (min(10, a) + min(10, c) + min(10, d)) % 10 == 0 || (min(10, a) + min(10, c) + min(10, e)) % 10 == 0 || (min(10, a) + min(10, d) + min(10, e)) % 10 == 0
                                || (min(10, b) + min(10, c) + min(10, d)) % 10 == 0 || (min(10, b) + min(10, c) + min(10, e)) % 10 == 0 || (min(10, b) + min(10, d) + min(10, e)) % 10 == 0 || (min(10, b) + min(10, d) + min(10, e)) % 10 == 0
                                || (min(10, c) + min(10, d) + min(10, e)) % 10 == 0)
                            {
                                int sum = min(10, a) + min(10, b) + min(10, c) + min(10, d) + min(10, e);
                                if (sum % 10 == 0) ans[a][b][c][d][e] = 30;
                                else if (sum % 10 >= 7) ans[a][b][c][d][e] = 2 * (sum % 10);
                                else ans[a][b][c][d][e] = sum % 10;
                            }
                        }
                    }
                }
            }
        }
    }
}
 
void RUN()
{
    Init();
    int t;
    scanf("%d", &t);
    while (t--)
    {
        int a, b, c, d;
        scanf("%d %d %d %d", &a, &b, &c, &d);
        int sum = 0;
        for (int i = 1; i <= 13; ++i) sum += ans[a][b][c][d][i];
        sum = (sum / 13.0) + 0.5;
        printf("%d\n", sum);
    }
}
 
int main()
{
#ifdef LOCAL_JUDGE
    freopen("Text.txt", "r", stdin);
#endif // LOCAL_JUDGE
 
    RUN();
 
#ifdef LOCAL_JUDGE
    fclose(stdin);
#endif // LOCAL_JUDGE
    return 0;
}

列舉最後一張牌，求總分，最後除以13

#include<bits/stdc++.h>
 
using namespace std;
 
int a[10], b[10];
int c[15];
 
void RUN()
{
    int t;
    scanf("%d", &t);
    while (t--)
    {
        for (int i = 1; i <= 4; ++i) scanf("%d", a + i);
        b[1] = min(10, a[1]) + min(10, a[2]);
        b[2] = min(10, a[1]) + min(10, a[3]);
        b[3] = min(10, a[1]) + min(10, a[4]);
        b[4] = min(10, a[2]) + min(10, a[3]);
        b[5] = min(10, a[2]) + min(10, a[4]);
        b[6] = min(10, a[3]) + min(10, a[4]);
        b[7] = 0;
        int tmp = 0;
        for (int i = 1; i <= 4; ++i) tmp += min(10, a[i]);
        for (int i = 1; i <= 4; ++i)
        {
            if ((tmp - min(10, a[i])) % 10 == 0)
            {
                b[7] = 1;
                break;
            }
        }
 
        double ans = 0;
        for (int i = 1; i <= 13; ++i)
        {
            a[5] = i;
            //1
            if (a[1] < 5 && a[2] < 5 && a[3] < 5 && a[4] < 5 && a[5] < 5 && a[1] + a[2] + a[3] + a[4] + a[5] <= 10)
            {
                ans += 60.0;
                continue;
            }
 
            //2
            if (a[1] >= 11 && a[2] >= 11 && a[3] >= 11 && a[4] >= 11 && a[5] >= 11)
            {
                ans += 50.0;
                continue;
            }
 
            //3
            if ((a[1] == a[2] && a[2] == a[3] && a[3] == a[4]) || (a[1] == a[2] && a[2] == a[3] && a[3] == a[5]) || (a[1] == a[2] && a[2] == a[4] && a[4] == a[5]) || (a[1] == a[3] && a[3] == a[4] && a[4] == a[5]) || (a[2] == a[3] && a[3] == a[4] && a[4] == a[5]))
            {
                ans += 40.0;
                continue;
            }
 
            //4
            int sum = 0;
            for (int i = 1; i <= 5; ++i) sum += min(10, a[i]);
            if (b[7])
            {
                if (sum % 10 == 0) ans += 30.0;
                else if (sum % 10 >= 7) ans += 2.0 * (sum % 10);
                else ans += sum % 10;
                continue;
            }
            //5
            int res = -1;
            for (int j = 1; j <= 6; ++j)
            {
                if ((b[j] + min(10, a[5])) % 10 == 0)
                {
                    res = sum % 10;
                    break;
                }
            }
            if (res == -1) continue;
            if (res == 0) ans += 30.0;
            else if (res >= 7) ans += 2.0 * res;
            else if (res != -1) ans += res;
        }
        ans = (ans / 13.0) + 0.5;
        printf("%d\n", (int)ans);
    }
 
}
 
int main()
{
#ifdef LOCAL_JUDGE
    freopen("Text.txt", "r", stdin);
#endif // LOCAL_JUDGE
 
    RUN();
 
#ifdef LOCAL_JUDGE
    fclose(stdin);
#endif // LOCAL_JUDGE
    return 0;
}

比賽的時候寫醜了，同時對於題意理解不明確？（說好的一副牌呢！）