代码太混乱且不合理,懒得改写了,你要对齐很简单,加了一句比较粗暴的语句即可实现,虽然很ugly,倒也可以应付你的文档了
begin{equation}
le{v_{a,b}}left({i,j} right)=
begin{cases}
max ({i,j}) &{hspace{-1.1cm}min({i,j})=0}\
min
begin{cases}
{le{v_{a,b}}left( {i - 1,j} right) + 1}\
{le{v_{a,b}}left( {i,j-1} right) + 1} &{else}\
{le{v_{a,b}}left( {i - 1,j - 1} right) + left[ {{a_i} ne {b_j}} right]}\
end{cases}
end{cases}
end{equation}