Yes, it is praise when someone tells you that you helped him or her solve a problem, and yes, it's good to feel joy with that. However, it's also good to be able to discriminate and understand that the praise is deserved, arising from something skillful, so that we don't just depend on the praise from that particular person to feel good about our actions. Feeling sympathetic joy with ourselves for being able to lessen the Dukkha of another person is very helpful. However, getting attached to praise and building our ego is not. So we have to have the wisdom to understand that the praise is deserving, and that it came from a good intention that we had, a compassionate intention. Then we understand the cause and effect relationship of things. As well as taking joy in the other person's ability to be grateful because this helps to be less dependent on the praise and more having joy with them and ourselves.