066dd615a6
Using recursion for reversing a String serves us no benifit. It places extra load on the stack, and it is less efficient than doing so iteratively. I understand now that we can not use built in reverse function, but using recursion is still the worst way we could do the task of String reversal. Everytime we call the reverse method we are placing an extra frame on our stack. This uses space. We also create another string that we are appending our result to with the recursive solution, which is slow because under the hood, Java will create a new empty String and then append each character to the new String, one char at a time. If we do this for each character, then asymtotically we now have time complexity of O(n^2). Recursion in this case also does not make our solution "simpler" or "more elegant". We want to use recursion when it is advantageous to do so....like traversing trees |
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| Conversions | ||
| data_structures | ||
| Searches | ||
| Sorts | ||
| .classpath | ||
| .DS_Store | ||
| .gitignore | ||
| .project | ||
| bfs.java | ||
| countwords.java | ||
| DecimalToOctal.java | ||
| dfs.java | ||
| Dijkshtra.java | ||
| Factorial.java | ||
| FindingPrimes.java | ||
| README.md | ||
| ReverseString.java | ||
The Algorithms - Java 
All algorithms implemented in Java (for education)
These are for demonstration purposes only. There are many implementations of sorts in the Java standard library that are much better for performance reasons.
Sort Algorithms
Bubble
From Wikipedia: Bubble sort, sometimes referred to as sinking sort, is a simple sorting algorithm that repeatedly steps through the list to be sorted, compares each pair of adjacent items and swaps them if they are in the wrong order. The pass through the list is repeated until no swaps are needed, which indicates that the list is sorted.
Properties
- Worst case performance O(n^2)
- Best case performance O(n)
- Average case performance O(n^2)
View the algorithm in action
Insertion
From Wikipedia: Insertion sort is a simple sorting algorithm that builds the final sorted array (or list) one item at a time. It is much less efficient on large lists than more advanced algorithms such as quicksort, heapsort, or merge sort.
Properties
- Worst case performance O(n^2)
- Best case performance O(n)
- Average case performance O(n^2)
View the algorithm in action
Merge
From Wikipedia: In computer science, merge sort (also commonly spelled mergesort) is an efficient, general-purpose, comparison-based sorting algorithm. Most implementations produce a stable sort, which means that the implementation preserves the input order of equal elements in the sorted output. Mergesort is a divide and conquer algorithm that was invented by John von Neumann in 1945.
Properties
- Worst case performance O(n log n)
- Best case performance O(n)
- Average case performance O(n)
View the algorithm in action
Selection
From Wikipedia: The algorithm divides the input list into two parts: the sublist of items already sorted, which is built up from left to right at the front (left) of the list, and the sublist of items remaining to be sorted that occupy the rest of the list. Initially, the sorted sublist is empty and the unsorted sublist is the entire input list. The algorithm proceeds by finding the smallest (or largest, depending on sorting order) element in the unsorted sublist, exchanging (swapping) it with the leftmost unsorted element (putting it in sorted order), and moving the sublist boundaries one element to the right.
Properties
- Worst case performance O(n^2)
- Best case performance O(n^2)
- Average case performance O(n^2)