shopee笔试求和那道题，用DP只对了75%，找不出疏漏

int main()
{
    int n, sum;
    cin >> n >> sum;

    for (int i = 0; i < n; i++)
    {
        int tmp;
        cin >> tmp;
        num.push_back(tmp);
    }

    vector<vector><int>> dp(num.size(), vector<int>(sum + 1, 0));
    // dp[i][j] 为以num[0..i]中数字组合出的和为j的组合数
    dp[0][num[0]] = 1;

    for (int i = 1; i < n; i++)
    {
        for (int j = 1; j <= sum; j++)
        {
            if (j - num[i] > 0)
                dp[i][j] = dp[i - 1][j - num[i]] + dp[i - 1][j];
            else if (j == num[i])
                dp[i][j] = dp[i - 1][j] + 1;
            else
                dp[i][j] = dp[i - 1][j];
        }
    }
    cout << dp[n - 1][sum] << endl;
    return 0;
}