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120 lines
3.0 KiB
Python
120 lines
3.0 KiB
Python
def print_dist(dist, v):
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"""
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Print vertex distance
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Examples:
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>>> print_dist([float('inf'),float('inf'),float('inf')], 3)
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<BLANKLINE>
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Vertex Distance
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0 INF
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1 INF
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2 INF
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>>> print_dist([2.0,6.0,10.0,3.0], 4)
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<BLANKLINE>
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Vertex Distance
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0 2
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1 6
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2 10
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3 3
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>>> print_dist([], 4)
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Traceback (most recent call last):
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...
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IndexError: list index out of range
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"""
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print("\nVertex Distance")
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for i in range(v):
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if dist[i] != float("inf"):
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print(i, " ", int(dist[i]), end="")
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else:
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print(i, " ", "INF", end="")
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print()
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def min_dist(mdist, vset, v):
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"""
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Finds the index of the node with the minimum distance between no-visited nodes
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Examples:
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>>> dist = [0.0, float('inf'), float('inf'), float('inf')]
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>>> set = [False, False, False, False]
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>>> min_dist(dist, set, 4)
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0
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>>> min_dist([], [], 0)
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-1
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"""
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min_val = float("inf")
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min_ind = -1
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for i in range(v):
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if (not vset[i]) and mdist[i] < min_val:
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min_ind = i
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min_val = mdist[i]
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return min_ind
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def dijkstra(graph, v, src):
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"""
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Dijkstra's algorithm to calculate the shortest distances from the src source node
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to all other nodes in a graph represented as an adjacency matrix.
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Examples:
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>>> G1 = [[0.0, 6.0, 2.0, float('inf')],
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... [float('inf'), 0.0, 9.0, 1.0],
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... [float('inf'), float('inf'), 0.0, 3.0],
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... [float('inf'), float('inf'), float('inf'), 0.0]]
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>>> dijkstra(G1, 4, 5)
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Traceback (most recent call last):
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...
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IndexError: list assignment index out of range
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>>> G2 = [[0.0, 6.0, 2.0, float('inf')],
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... [float('inf'), 0.0, 9.0, 1.0],
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... [float('inf'), float('inf'), 0.0, 3.0],
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... [float('inf'), float('inf'), float('inf'), 0.0]]
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>>> dijkstra(G2, 4, 0)
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<BLANKLINE>
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Vertex Distance
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0 0
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1 6
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2 2
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"""
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mdist = [float("inf") for _ in range(v)]
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vset = [False for _ in range(v)]
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mdist[src] = 0.0
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for _ in range(v - 1):
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u = min_dist(mdist, vset, v)
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vset[u] = True
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for i in range(v):
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if (
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(not vset[i])
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and graph[u][i] != float("inf")
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and mdist[u] + graph[u][i] < mdist[i]
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):
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mdist[i] = mdist[u] + graph[u][i]
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print_dist(mdist, i)
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if __name__ == "__main__":
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import doctest
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doctest.testmod(verbose=True)
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V = int(input("Enter number of vertices: ").strip())
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E = int(input("Enter number of edges: ").strip())
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graph = [[float("inf") for i in range(V)] for j in range(V)]
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for i in range(V):
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graph[i][i] = 0.0
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for i in range(E):
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print("\nEdge ", i + 1)
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src = int(input("Enter source:").strip())
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dst = int(input("Enter destination:").strip())
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weight = float(input("Enter weight:").strip())
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graph[src][dst] = weight
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gsrc = int(input("\nEnter shortest path source:").strip())
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dijkstra(graph, V, gsrc)
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