f(x,y)={x+1x<yxx=yx=1x>yf(x,y)=\begin{cases}x+1 & x<y\\x & x=y\\x=1 & x>y\end{cases}f(x,y)=⎩⎨⎧x+1xx=1x<yx=yx>y
应改为
f(x,y)={x+1x<yxx=yx−1x>yf(x,y)=\begin{cases}x+1 & x<y\\x & x=y\\x-1 & x>y\end{cases}f(x,y)=⎩⎨⎧x+1xx−1x<yx=yx>y
$f(x,y)=\begin{cases}x+1 & x<y\\x & x=y\\x-1 & x>y\end{cases}$
