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Commit e52c94e

Browse files
algorithms
1 parent 878cb39 commit e52c94e

21 files changed

+374
-0
lines changed

‎competitivepython/graphs/__init__.py

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# __init__.py
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from .bfs import breadth_first_search
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from .dfs import depth_first_search
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from .dijkstra import dijkstra
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__all__ = ['breadth_first_search', 'depth_first_search', 'dijkstra']
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‎competitivepython/graphs/bfs.py

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def breadth_first_search(graph, node):
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visited, queue = set(), [node]
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visited.add(node)
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while queue:
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vertex = queue.pop(0)
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visited.add(vertex)
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for neighbour in graph[vertex]:
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if neighbour not in visited:
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queue.append(neighbour)
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return visited

‎competitivepython/graphs/dfs.py

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def depth_first_search(graph, node):
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visited = set()
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visited = dfs_helper(graph, node, visited)
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return visited
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def dfs_helper(graph, node, visited):
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if node not in visited:
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visited.add(node)
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for neighbour in graph[node]:
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dfs_helper(graph, neighbour, visited)
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return visited

‎competitivepython/graphs/dijkstra.py

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import heapq
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def dijkstra(graph, start, end):
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distances = {vertex: float('inf') for vertex in graph}
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distances[start] = 0
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path = {vertex: [] for vertex in graph}
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queue = [(0, start)]
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while queue:
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(current_distance, current_vertex) = heapq.heappop(queue)
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if current_vertex == end:
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break
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for neighbor, weight in graph[current_vertex].items():
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distance = current_distance + weight
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if distance < distances[neighbor]:
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distances[neighbor] = distance
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heapq.heappush(queue, (distance, neighbor))
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path[neighbor] = path[current_vertex] + [neighbor]
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return {'distance': distances[end], 'path': path[end]}
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def kmp_search(pat, txt):
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M = len(pat)
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N = len(txt)
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# create lps[] that will hold the longest prefix suffix
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# values for pattern
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lps = [0] * M
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j = 0 # index for pat[]
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# Preprocess the pattern (calculate lps[] array)
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computeLPSArray(pat, M, lps)
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i = 0 # index for txt[]
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indices = []
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while i < N:
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if pat[j] == txt[i]:
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i += 1
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j += 1
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if j == M:
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indices.append(i - j)
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j = lps[j - 1]
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# mismatch after j matches
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elif i < N and pat[j] != txt[i]:
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# Do not match lps[0..lps[j-1]] characters,
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# they will match anyway
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if j != 0:
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j = lps[j - 1]
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else:
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i += 1
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return indices
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def computeLPSArray(pat, M, lps):
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len = 0 # length of the previous longest prefix suffix
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lps[0] = 0
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i = 1
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# the loop calculates lps[i] for i = 1 to M-1
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while i < M:
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if pat[i] == pat[len]:
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len += 1
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lps[i] = len
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i += 1
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else:
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# This is tricky. Consider the example.
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# AAACAAAA and i = 7. The idea is similar
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# to search step.
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if len != 0:
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len = lps[len - 1]
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# Also, note that we do not increment i here
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else:
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lps[i] = 0
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i += 1
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‎competitivepython/searches/__init__.py

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# __init__.py
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from .binarysearch import binary_search
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from .linearsearch import linear_search
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from .KMP_pattern_search import kmp_search
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__all__ = ['binary_search', 'linear_search', 'kmp_search']
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def binary_search(arr, target):
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left, right = 0, len(arr) - 1
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while left <= right:
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mid = left + (right - left) // 2
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if arr[mid] == target:
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return mid
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elif arr[mid] < target:
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left = mid + 1
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else:
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right = mid - 1
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return -1
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def linear_search(arr, target):
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for search in range(len(arr)):
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if arr[search] == target:
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return search
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return -1

‎competitivepython/sorting/__init__.py

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# __init__.py
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from .bubblesort import bubble_sort
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from .insertionsort import insertion_sort
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from .shellsort import shell_sort
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from .selectionsort import selection_sort
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from .bucketsort import bucket_sort
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from .mergesort import merge_sort
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from .timsort import tim_sort
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from .quicksort import quick_sort
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from .heapsort import heap_sort
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from .radixsort import radix_sort
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__all__ = ['bubble_sort', 'insertion_sort', 'shell_sort', 'selection_sort',
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'bucket_sort', 'merge_sort', 'tim_sort', 'quick_sort', 'heap_sort', 'radix_sort']

‎competitivepython/sorting/bubblesort.py

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def bubble_sort(arr):
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length = len(arr)
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for i in range(length):
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for j in range(0, length-i-1):
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if arr[j] > arr[j+1]:
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arr[j], arr[j+1] = arr[j+1], arr[j]
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return arr

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