Algorithms

Algorithms is one of the most important area of computer science. If one wish to be successful in CS then he must work hard on algorithms. They are a bit trickier than any other topics and need lot of focus right from basics. 

Regarding GATE, algorithms always played and will play an important role. The syllabus for algorithms in gate exam is

Analysis, Asymptotic notation, Notions of space and time complexity, Worst and average case analysis; Design: Greedy approach, Dynamic programming, Divide-and-conquer; Tree and graph traversals, Connected components, Spanning trees, Shortest paths; Hashing, Sorting, Searching. Asymptotic analysis (best, worst, average cases) of time and space, upper and lower bounds, Basic concepts of complexity classes – P, NP, NP-hard, NP-complete.

For preparation, i suggest to group the topics this way - 

Group A  : (Need less time to finish, stress on basics, work on lot of example codes)
Asymptotic notation, Notions of space and time complexity, Worst and average case analysis, Asymptotic analysis (best, worst, average cases) of time and space, upper and lower bounds.

Group B : (Interesting, takes time to understand, stress on greedy and DAC)
Greedy approach, Dynamic programming, Divide-and-conquer

Group C : (Takes time to complete, easy to understand,  
 Tree and graph traversals, Connected components, Spanning trees, Shortest paths; Hashing, Sorting, Searching

Group D : (Takes less time, it may confuse few, do not try to over emphasize and waste time but do not skip)
complexity classes – P, NP, NP-hard, NP-complete.

You can find some references below

Worst and average case analysis

Comparision of various algorithms

Greedy Approach

Fractional Knapsack problem
Job Sequencing with deadlines

Sorting 

Bubble sort

Selection sort