County were trailing until the 89th minute when De Leeuw headed them level before the Dutchman crossed for Richie Brittain to bag the winner.
"I'm delighted for him because he's had to wait for his opportunity but we've got high hopes for him," said Adams.
"Over the 90 minutes, I thought we played well. We created openings."
Callum Paterson had put Hearts ahead and Adams praised the travelling fans for the backing they gave their team at Victoria Park.
"They were fantastic from start to finish and if I was the manager of Hearts, I'd be delighted with the support that they get because if I'm a player, I feed off that," he said.
"Obviously we fed off that as well over the 90 minutes. They're great for their club, they're a credit to their football club.
"Hearts were terrific at times and we dealt with whatever they put up against us but I think we deserved to take something out the game, there's no doubt about that."
Hearts boss Gary Locke added: "It's a sore one, a real kick in the teeth for us. I thought at 1-0 we looked really comfortable and I could not see them scoring.
"When you get to the last kick of the ball you have got to defend better than that. We can't feel sorry for ourselves. We have got to pick ourselves up and go again on Wednesday night."