$f:N\rightarrow Z$ is a function defined as $f(n)=\left\{ \begin {array} {1 1} \large\frac{n-1}{2}, \:\:when\:\: n\:\: is\:\: odd \\ -\large \frac{n}{2},\:\:when\:\: n\:\: is\:\: even \\ \end{array} \right.$, then $f$ is

Question

$\begin{array}{1 1} neither\;1-1\;nor\;onto \\ many \;to\;one\;onto \\ 1-1 \;but\;not\;onto \\ both \;1-1\;and\;onto \end{array}$