Implement One-Hot Encoding

Implement one-hot encoding.

Convert integer class labels into one-hot vectors. Each label $i$ becomes a vector of length num_classes with 1 at position $i$ and 0 everywhere else.

Input:

• labels: 1D integer tensor of shape (N,) with values in $[0, \text{num\_classes})$
• num_classes: total number of classes

Output: 2D tensor of shape (N, num_classes) with one-hot encoding