Veg is great for supplementary feeding, and adds flavour to the meat, as well as giving interest to the pigs, and I'm all in favour of it.
However you should be conscious of what your pigs need
Food consists of Energy (typically lipids & carbohydrates), protein, vitamins, minerals and water
Pigs need the right balance of these, and for growing they need not only protein, but the right kind of protein.
Veg will be good at delivering vitamins and in many cases the minerals, some is good at carbohydrate, and all are good with water, some more than others - eg cucumber !
However most veg is bad at delivering protein, and in the case of pigs the right balance of proteins.
Commercial pig food will almost always contain soya, at that is the closest to the pig's needs for protein, but even this lacks some essential amino acids (building blocks of protein), which are added to the feed such as lysine. In the old days when swill was fed, this had meat content, which is where pigs got the protein from.
Now protein is what grows your pigs, protein = muscle. So if you start to feed lots of veg to growing pigs, you can slow their growth, which means that you will be feeding them longer. So if you are doing this to save money, rather than add flavour, the maths may not work out in your favour.
In the worst case mineral and vitamin deficiency can give them issues, such as bone defects. Now don't panic ! You're unlikely to do the latter if you are feeding pig nuts alongside, and even if you fed exclusively veg it would depend on what veg you are feeding them.
For dry sows who need energy rather than growth, when we have veg, we tend to feed one meal as nuts and the other as veg, that way at least they are getting one fully balanced meal a day.
The point of all the above is that there are rules of thumb, such as 4 times the weight of veg to nuts, but these are rough guides, intended for occasional use.
If you are going to feed significant amounts of veg to growing pigs as a major part of their diet, then you should do some research into pig diets - The best book I know is "The Nutrition and feeding of organic pigs" by Robert Blair. At £57.50 it is not cheap, but if you save 8 25kg feed sacks you've paid for the book ! Feeding Organic Pigs by Newcastle university is also very good.