Categories

Searching

Searching an element from a set of elements

Sorting

Sorting a set of elements in a particular order

Stack and Queue

Algorithms that require FIFO or LIFO processing

Trees

Segment trees, BITs and other algorithms for interval processing and searching

Graphs

Modelling real life problems as a set of vertices and links between them

Greedy and Dynamic Programming

Solving a bigger problem through solution of subproblems

Others

Any algorithm that doesn't come under the above categories