cases公式第一行空白太大 about thesisuestc HOT 5 CLOSED

分段函数测试：
    {\vspace{-18pt}\singlespacing\[
      \begin{cases}
        f_{i,j,s}^k\leftarrow d_{i,j}^k/\sigma,~d_{i,j}^k\leftarrow d_{i,j}^k - f_{i,j,s}^{k} \\
        x(p_{i,j,s}^k)\leftarrow x(p_{i,j,s}^k) + f_{i,j,s}^k
      \end{cases}
      , \forall k\in\kappa(u_j)
      \]
    }

分段函数测试2：
    {\vspace{-20pt}\singlespacing
      \begin{equation}
      f_n(\mb{r})=
      \begin{cases}
      \frac{l_n}{2A_n^+}\mb{\rho}_n^+=\frac{l_n}{2A_n^+}(\mb{r}-\mb{r}_+)&\mb{r}\in T_n^+\\
      \frac{l_n}{2A_n^-}\mb{\rho}_n^-=\frac{l_n}{2A_n^-}(\mb{r}_--\mb{r})&\mb{r}\in T_n^-\\
      0&\text{otherwise}
      \end{cases}
      \end{equation}
    }