There are many algorithms available for a computer programmer to solve a Sudoku.
Just google it some time and I’m sure you will find an abundance of resources.
Some algorithms take a very long time to solve a Sudoku and others will have an answer within milliseconds. It all depends on the approach.
The same can be said about people who solve Sudokus. Some people can solve a Sudoku very quickly while others find it hard to even solve the lowest grade Sudoku available. It’s all about insight and pattern spotting.