Brute force algorithm:-
Brute force implies using the definition to solve the problem in a straightforward manner.
Brute force algorithms are usually the easiest to implement, but the disadvantage of solving a problem by brute force is that it is usually very slow and can be applied only to problems where input size is small.
Divide and conquer algorithm:-
In divide and conquer method, we divide the size of a problem by a constant factor in each iteration. This means we have to process lesser and lesser part of the original problem in each iteration. Some of the fastest algorithms belong to this class. Divide and conquer algorithms have logarithmic runtime.
Decrease and conquer algorithm:-
This kind of problem is same as divide and conquer, except, here we are decreasing the problem in each iteration by a constant size instead of constant factor.
Read more at http://gonitsora.com/algorithm-types-and-classification/#TdZOUE8KelEImvTA.99